Pitcher Joe Ross fields a ball while running through a defensive drill Friday. (Toni L. Sandys/The Washington Post)
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Southpaw Patrick Corbin, who fanned 246 batters last season, and catcher Yan Gomes, who hit 16 homers, were all-stars at last season's game at Nationals Park.

Brian Dozier, Trevor Rosenthal and Kurt Suzuki also have been all-stars. Dozier hit 42 and 34 homers in 2016 and 2017, respectively. Rosenthal, just 28, saved 45 and 48 games in consecutive seasons and was a standout in a World Series. In the past two years in 623 at-bats, Suzuki hit 31 homers with 100 RBI and an .825 on-base-plus-slugging percentage.

Anibal Sanchez and Max Scherzer were teammates in Detroit from 2012 to 2014. And when Scherzer won his first Cy Young in 2013, Sanchez won the ERA title (2.57) that season. Last year, Sanchez’s ERA was 2.83.

In the past two years, in 645 at-bats, Matt Adams has 41 homers and 122 RBI. In his career, Kyle Barraclough has a 3.21 ERA with 279 strikeouts in 218 ⅔ innings.

All of them are new Washington Nationals, all added in one offseason.

Sometimes I’m not entirely sure everyone is paying full attention. Especially when I see Las Vegas odds say the Nats are in a three-way tie as the ninth-best team in MLB with mundane 16-1 odds to win the World Series.

“You look at this team, and there really isn’t a weakness,” said Corbin, who signed a six-year, $140 million contract as a free agent, which remains more money than the next two most lucrative signings of this offseason combined.

The Nats will have everything they can handle — and maybe more — just to win the National League East from the defending champ Braves and the much-improved Phillies and Mets. It should be a lovely six-month battle.

With so many games against tough division rivals, it will be especially tough for NL East teams to win enough games to get a wild-card spot. So this could get ugly. That’s why it’s easy to lump the Nats, minus the flashy Bryce Harper, who hasn’t been in the Nats’ plans for months, among the teams with a great deal to prove.

But the Nats are also a potentially exceptional team that is now in Florida trying to shed its slipshod ways of 2018 when gruesome defense, air-headed base running, some disappointing starting pitching, unsound fundamentals, a raw rookie manager — is this list long enough? — plus a lot of injuries produced an ­82-80 season that Scherzer calls “a terrible year.”

“Pitching, defense and athleticism has been our credo for 12 years,” said General Manager Mike Rizzo, who thinks his team drifted from those core values. “Last year, there were reasons our defense wasn’t very good. Our record in one-run games [18-24] showed it. We gave too many teams 28, 29, 30 outs, and we gave away outs with our base running. This year, we’ll be much better. We have to be.

It will help that Daniel Murphy, who started only one double play in 36 starts at second base, has taken his bat to Colorado to play first base. And it will help that Harper, team-spirited enough to play out of position in center field in 63 games, won’t be gumming up the works with his starkly deteriorating defense.

Team leadership has been, off and on, an issue for the Nats for years. Every championship club needs at least a half-dozen future managers in its clubhouse to demand accountability and constantly raise the team’s baseball IQ. Those players, such as Jayson Werth, may never manage a game anywhere except in Little League for one of their kids. But everyone in the room knows that they could become respected managers if they chose to be.

Last season, after Howie Kendrick was lost for the season to injury, the Nats were down to Scherzer and Adam Eaton as the two fully engaged and demanding team leaders. The night reliever Shawn Kelley showed up Martinez by slamming his glove on the ground and glaring into the dugout after giving up a homer — as if he were a big star who merited better than mop-up duty — people with knowledge of the Nationals say Max and Mighty Mouse were waiting for him in the tunnel after the game to chew him out.

This year, they may have company. Kendrick is back. “He was a huge loss for us,” Rizzo said.

Dozier always has been a heady team leader. When the Nats asked Scherzer about Sanchez’s clubhouse makeup, Scherzer raved about him being a “great glue guy in the clubhouse” who unites factions and organized team dinners. And he was a savvy teacher, too. “Taught me some things,” Scherzer said.

Gomes and Suzuki “check those boxes,” according to Rizzo, as student-of-the-game players who demand alertness and hustle from others.

Though few mention it, subtracting Harper, while it will cost 34 homers, a .899 career OPS and some amazing hair flips, would help any team improve its attention to fundamentals. When the most famous player on the team can’t go 10 days without failing to run out a groundball or overthrowing a cutoff man by 15 feet or throwing to the wrong base or being caught unprepared in the outfield or on the bases, it’s hard to demand total alertness from the other 24.

“Write it,” one prominent Nats vet said.

Losing Harper carries a high cost. But if the Nats don’t play a crisper, less mistake-riddled brand of baseball without him, it’s an opportunity wasted. Rizzo has done many things right, but in Bryce’s early years, when he had “players’ managers” who rarely said a discouraging word and owned no whip, Rizzo should have been the bad cop to tell him the truth about the gaps in his game. But the GM had such a high opinion of Harper personally — always referred to as “such a great kid” — that he couldn’t make the leap to “but also an overindulged player.”

Perhaps Rizzo and the Nats made a mistake in thinking that a club that tested Dusty Baker’s patience could be handled and shaped up by any rookie manager.

Now, a year later, the Nats and Martinez are focused on what should have obsessed them last year in their cheery training camp: basics. You can ride camels and have golf-shot games after you prove you consistently play the game right.

“We’re going to be more proactive on fundamentals,” Martinez said this week. “There will be days when they don’t bring their bats to the field. It will all be team defense, base running and fundamentals. They can still hit in the cage.”

Martinez has reiterated his belief that teams don’t need to work long hours in spring training if their work is crisp and precise. This year, he’s added a twist: “If we don’t do it right, then the days will get long.” Well, better late than never.

This is a Nats team with few weaknesses, a dominant top three in its rotation and justified reasons for high hopes. But it is also a club that will sink if it repeats its mental gaffes and fundamental laxness from last season’s embarrassment.

Out of necessity, improvement. Or that’s the idea, anyway.

For more by Thomas Boswell, visit washingtonpost.com/boswell.