Jake Arrieta set a standard in 2015 that will be almost impossible to match. (Jonathan Daniel/Getty Images)

In the four-year history of baseball’s current postseason format, only the National League Central has produced three playoff teams in one year — first in 2013, and then again last season, when the upstart Cubs joined St. Louis and Pittsburgh, then outlasted both of them in the playoffs.

Now, Chicago enters the season not as a team that might be good in a year or two. They enter what might be the most anticipated season on Chicago’s North Side as — gulp — favorites, both because of what they did last year on the field (winning 97 games) and what they did over the winter in taking the game’s best young core and improving it.

A pre-spring training look at the division, which might have three playoff contenders again.

Chicago Cubs

2015 record and finish: 97-65, third in division, lost to New York Mets in NLCS

2016 FanGraphs projection: 94-68, first

Significant additions: OF Jason Heyward, IF/OF Ben Zobrist, SP John Lackey, RP Adam Warren

Significant losses: SS Starlin Castro, CF Dexter Fowler, OF Chris Denorfia, OF Austin Jackson

Why they’ll win the division: They won 97 games in their coming-out year, then stole from the team that has won three straight division titles.

Had the Cubs simply added Heyward and Lackey in a vacuum, their offseason could have been called a success, because they added arguably the most valuable free-agent position player on the market (Heyward was worth 6.0 wins above replacement (WAR) in 2015, according to FanGraphs) and the veteran starter they needed behind Cy Young winner Jake Arrieta and Jon Lester (Lackey was worth 3.6 WAR). But the Cubs didn’t land those two players — the 26-year-old Heyward for eight years and $184 million, Lackey for two years and $32 million — in a vacuum. They took them directly from the Cardinals, the team the 2015 Cubs ousted from the postseason. The team with the best young core in baseball — a core so good that they could trade a 25-year-old three-time all-star shortstop (Castro, who went to the Yankees for Warren) just so they could fit all their pieces — added to its offense, defense, rotation and bullpen. A pitch hasn’t been thrown yet. Find the weakness.

Most significant question: Was that the real Jake Arrieta?

In the first 69 outings of his career — 63 of them starts, all with the Baltimore Orioles from 2010-13 — Arrieta rang up a 5.46 ERA and allowed an astronomical 1.472 walks and hits per inning pitched. And then in 2015, he became … Cy Young? (His 22-6, 1.77 ERA, 0.865 WHIP season looks incredible in its entirety, but remember that in 12 starts in August and September, he allowed four earned runs total for a 0.41 ERA and .136 batting average against, and it’s just staggering.) Now, Arrieta is coming off a season in which he threw 238 2/3 innings in the regular and postseasons — 83 more than he had ever thrown in a season before. Can he approach his 2015 level again?

Spring training battle to watch: Jason Heyward vs. center field

Heyward has made 781 starts in the outfield in his career — 751 of them in right field. He is a Gold Glove winner in the corner, perhaps the best right fielder in the game. But the Cubs appear ready to use him primarily in center. The problem is obvious: They want the bats of Kyle Schwarber (16 homers in his first 273 plate appearances last summer) and Jorge Soler to develop in left and right, respectively. Heyward is the best defender of the bunch, and it’s not close; the other two are liabilities. But how will Heyward adapt to a full-time role in center, and what will the Cubs look like defensively late in games when they’re protecting a lead?

Did you realize?: The Cubs allowed 608 runs last season (3.75/game), their fewest in any season not shortened by labor strife since 1972. Only the Cardinals, Dodgers and Pirates allowed fewer in 2015.

St. Louis Cardinals

2015 record and finish: 100-62, won the NL Central, lost to Cubs in NLDS

2016 FanGraphs projection: 84-78, tied for second

Significant additions: SP Mike Leake, IF Jedd Gyorko, RP Seung-Hwan Oh

Significant losses: OF Jason Heyward, SP John Lackey, OF Jon Jay, OF Peter Bourjos

Most significant question: Can this lineup score enough?

Even with ace Adam Wainwright sidelined virtually all season by an Achilles injury — he made four starts early, then three late-season relief appearances — St. Louis led all of baseball in run prevention, allowing just 3.24 a game, the lowest of any team in a 162-game season since 1972. Yes, Lackey departed for Chicago, but 28-year-old Leake essentially takes his place. The Cardinals grow bullpen arms like weeds, so preventing the opposition from scoring shouldn’t be an issue. But a lineup that outscored just six teams in baseball loses Heyward and adds — Gyorko? Yes, they’ll get a full season out of midseason acquisition Brandon Moss, who will in turn be pitted against incumbent Matt Adams (coming back from a torn quadriceps muscle) in a battle for the first base job. But there are legitimate questions about the consistency of their production.

Spring training battle to watch: Yadier Molina vs. his thumb

The Cardinals’ catcher means so much to the team’s entire operation that if he struggles to come back from October thumb surgery, it could slow down the team’s development. Molina is due to have the cast removed from his left thumb in mid-February, and from there his return will depend on how quickly he can restore strength. Molina’s .660 OPS in 2015 was his lowest since 2006, but he must be healthy to handle the Cardinals’ pitching staff.

Did you realize?: When Mike Matheny replaced Hall of Famer Tony La Russa after the Cardinals’ 2011 World Series title, there was little way to know what the results might be because Matheny hadn’t managed at any level. But he’s the only manager we can find who has led his team to the postseason in his first four major-league seasons — first as a wild card in 2012, then the past three division titles.

Pittsburgh Pirates

2015 record and finish: 98-64, second, lost to Cubs in first-round

2016 FanGraphs projection: 84-78, tied for second

Significant additions: SP Jon Niese, SP Ryan Vogelsong, 1B/C John Jaso, RP Neftali Perez, RP Juan Nicasio

Significant losses: 2B Neil Walker, SP A.J. Burnett, RP Antonio Bastardo, RP Joakim Soria, 1B/3B Pedro Alvarez, 3B Aramis Ramirez, SP Charlie Morton

Most significant question: Is this rotation good enough for a fourth straight postseason berth?

Last year, Pirates’ starting pitchers posted the fifth-best ERA in baseball and were fourth in the NL in both innings pitched and strikeouts per nine innings. But A.J. Burnett retired, Morton was dealt to Philadelphia and trade-deadline savior J.A. Happ (1.85 ERA in 11 starts for Pittsburgh) left for Toronto via free agency. The front of the rotation remains solid, with Gerrit Cole from the right side and Francisco Liriano from the left. But after that? Jeff Locke will get yet another chance after a lousy year (4.49 ERA, 1.420 WHIP). Niese, who had no place in the crowded Mets’ rotation, is reliable but not flashy; his 59-59 record with a 3.86 ERA since he became a full-time starter in 2010 is almost the definition of ordinary. Vogelsong is 38 and coming off a year in which he had a 4.67 ERA and 1.467 WHIP for the Giants. Scarier for Pittsburgh fans: His numbers away from AT&T Park were horrific — 5.90 ERA, 1.638 WHIP and a .300 batting average/.873 OPS against. If the Pirates are in it at the trade deadline again, expect them to search for help in the rotation.

Spring training battle to watch: Jung-Ho Kang vs. his left leg

Kang was in the midst of a fine rookie season when he was taken out at second base in September, breaking his leg. He’ll enter spring training extremely limited, but he has pledged to try to be back by Opening Day. But given the departures of Walker and Alvarez and the relatively little impact the Pirates brought in offensively, Kang’s development from a rookie year in which he hit .287 with an .816 OPS and 15 homers is important.

Did you realize?: Since breaking a 20-year playoff drought, the Pirates have averaged better than 93 wins over the past three seasons. The only team to win more games since 2013? The Cardinals, which beat the Pirates for the division title each time. Pittsburgh has appeared in the NL first-round playoff game in three straight seasons, losing to Madison Bumgarner in 2014 and Jake Arrieta last October.

Milwaukee Brewers

2015 record and finish: 68-94, fourth

2016 FanGraphs projection: 70-92, fifth

Significant additions: 1B Chris Carter, 3B Will Middlebrooks, IF Aaron Hill, OF Kirk Nieuwenhuis, IF Jonathan Villar, OF Ramon Flores

Significant losses: RP Francisco Rodriguez, 1B Adam Lind, SS Jean Segura, OF Logan Schafer

Most significant question: How much longer will Jonathan Lucroy and Ryan Braun be Brewers?

New general manager David Stearns, who graduated from Harvard just in 2007, came from the Astros, where he worked under Jeff Luhnow. Luhnow’s model was simple: Lose, and lose big — 416 games in four seasons before reaching the playoffs last year. Stearns sold off what few assets he could — Rodriguez, the closer, traded to Detroit and Lind, sent to Seattle. But the big chips remain. Lucroy is coming off a down season (.717 OPS) that ended with a concussion, but he remains a valuable catcher who is due only $5.25 million on a club option for 2017, what would be his first year of free agency. Braun, 32, is a six-time all-star and former MVP who has defined this era of baseball in Milwaukee. His five-year, $105 million contract kicks in this year — and includes no-trade protection. He’ll be harder to deal for those reasons — not to mention that he is coming off back surgery and was suspended following the Biogenesis investigation, so there are other hurdles.

Spring training battle to watch: Matt Garza vs. the Brewers

The one-time ace lost his job in the rotation and then left the club to be with his pregnant wife, ending the worst season of his major league career with a 5.63 ERA — the only time his full-season ERA has been higher than 3.91. He is due $12.5 million in each of the next two years, but interestingly, he has a $13-million option for 2018 that kicks in if he makes 110 starts from 2014-17 and pitches at least 115 innings in 2017. He has 52 starts in the first two years. Will this relationship be healed to the point where Garza returns to the rotation? Will he pitch better when he gets there? And how will that impact the Brewers in the future?

Did you realize?: The Brewers’ collective on-base percentage last year (.307) was their lowest since 1972. They gave 975 plate appearances to two players — second baseman Scooter Gennett and shortstop Jean Segura — who posted OBPs of .295 and .281, respectively. As part of Stearns’s rebuild, Segura was shipped to Arizona in a deal that centered around 19-year-old shortstop prospect Isan Diaz. (The trade brought back 34-year-old veteran Aaron Hill, whose OBP last year was .295.)

Cincinnati Reds

2015 record and finish: 64-98, fifth

2016 FanGraphs projection: 73-89, fourth

Significant additions: IF Jose Peraza, OF Scott Schebler

Significant losses: RP Aroldis Chapman, 3B Todd Frazier, OF/IF Skip Schumaker, C Brayan Pena

Most significant question: How much longer will Jay Bruce and Brandon Phillips be Reds?

Cincinnati’s rebuilding effort began last summer, when the Reds traded ace Johnny Cueto, fellow starter Mike Leake and outfielder Marlon Byrd. They dealt Chapman, one year till free agency, to the Yankees for prospects in the offseason. A three-team deal sent Frazier, an all-star last year, to the White Sox and brought back prospects Peraza and Schebler, either of whom could play in the majors this year. Now, two tradable mainstays remain. Phillips, Cincinnati’s regular second baseman since 2006, has the right to waive any trade — and he did so over the winter, squelching a deal that would have sent him to Washington. He could be difficult to move. But Bruce should be gone. He is coming off two dismal seasons — .222 average with a .288 OBP and .406 slugging percentage in 2014-15 — and makes $12.5 million this year with a $1 million buyout of 2017. But he turns just 29 in April and offers the rarest commodity in the game at the moment — power (26 homers last season).

Spring training battle to watch: Bryan Price vs. the rebuild

The Reds made three playoff appearances between 2010-13, and the response was to fire Dusty Baker as manager. They replaced Baker with his pitching coach, Bryan Price, who oversaw a lousy season in 2014 and a disastrous one in 2015. Yet Price was invited back for the upcoming year, which figures to be difficult to watch. How can managers be evaluated in situations in which their club is at a talent deficit? We’ll leave that to Walt Jocketty, the club’s president of baseball operations, and new general manager Dick Williams.

Did you realize?: First baseman Joey Votto reached base at a remarkable .535 clip in the second half of the 2015 season. Players, in history, to top that mark in any second half of a season in their career: Barry Bonds (four times, including .608 in 2002), Ted Williams (twice), Babe Ruth (three times) and Rogers Hornsby (once). With Frazier now gone and Votto likely to see even fewer pitches, could he top that this season?

The Post’s Preseason Picks Series

Monday: National League East

Tuesday: National League Central

Wednesday: National League West

Feb. 15: American League East

Feb. 16: American League Central

Feb. 17: American League West