The trade deadline could be high profile, especially if the New York Mets decide to deal Jose Reyes. (Norm Hall/GETTY IMAGES)

Was 2010 really the Year of the Pitcher, as it was frequently called, or perhaps the start of the Era of the Pitcher? The first half of 2011 certainly suggested the latter. Run-scoring reached its lowest level since 1992, leading to some eye-popping statistics — both low ERAs and low batting averages — and perhaps accelerating the growing parity in the game. When offense is down across the board, games are closer and less distance separates the best from the worst.

Here are five story lines to watch in baseball as the second half opens Thursday:

Division races: This sets up as one of the best, most competitive stretch drives in recent memory. None of the six first-place teams at the break owns a lead larger than 31 / 2 games (and in four divisions, the leaders are separated by a single game or less), while no fewer than 20 teams are within eight games of a playoff spot (including your Washington Nationals, who are eight games in back of Atlanta in the NL wild card race). Virtually every day the rest of the regular season will feature at least one meaningful, intradivisional matchup.

Making the pennant race even richer in story lines is the fact four teams that lost at least 93 games in 2010 – the Indians, Pirates, Mariners and Diamondbacks — are within striking distance of a playoff spot. Of these, the Pirates deserve a special mention: After 18 consecutive losing seasons, the longest such stretch in professional sports, they enter the season’s second half just one game behind NL Central co-leaders Milwaukee and St. Louis.

Trade deadline: The last two Julys have featured blockbuster trades centered around lefty Cliff Lee. This time, it is safe to say Lee is staying put in Philadelphia, and there don’t appear to be any game-changing, No. 1 starters available in this trade market, as the July 31 deadline approaches.

But it could still be a highly active and high-profile trade-deadline season, especially if the Mets decide to trade shortstop Jose Reyes and/or right fielder Carlos Beltran. Other big names that may or may not be available: Hunter Pence (Astros), Anibal Sanchez (Marlins), Hanley Ramirez (Marlins), Aramis Ramirez (Cubs) and Ubaldo Jimenez (Rockies).

Meantime, the Nationals, with a roster stacked with productive veterans, could be at the epicenter of the trade market, with the possible trade targets including starters Jason Marquis and Tom Gorzelanny, relievers Sean Burnett and Todd Coffey, outfielder Laynce Nix and catcher Ivan Rodriguez.

Pitching landmarks: With league-wide runs-per-game (8.36) at its lowest level since 1992, reflecting the growing dominance of pitching in today’s game, it is no wonder there are some landmark pitching achievements within reach this season.

Baseball hasn’t had more than nine 20-game winners in a season since 1974, but 13 pitchers reached the break with 10 wins (and another eight have nine wins). Tops among them is New York Yankees lefty CC Sabathia, with 13 wins – followed by Justin Verlander and Jair Jurrjens with 12 each — giving one or all a shot at becoming the first 25-game winners since Oakland’s Bob Welch in 1990.

At the same time, baseball hasn’t seen a qualifying pitcher post a sub-2.00 ERA over a full season since Boston’s Pedro Martinez in 2000. But Jered Weaver of the Los Angeles Angels (1.86) and Atlanta’s Jurrjens (1.87) both arrived at the all-star break below that magical threshold.

The abyss: Is it possible Chicago White Sox designated hitter Adam Dunn, formerly of the Nationals, is constructing one of the worst offensive seasons in modern baseball history? Yes, if his first-half performance (.160 batting average, .597 OPS, 117 strikeouts) carries through the second half.

No batter with a qualifying number of plate appearances has posted a batting average lower than .179 (Rob Deer, 1991) since 1900. And only Arizona’s Mark Reynolds in 2010 has combined a sub-.200 batting average (.198) with more than 200 strikeouts (211). Amazingly, Dunn has only two hits all year off lefties, resulting in a .031 batting average – which would obliterate the low-water mark achieved by Texas’s Benji Gil (minimum 100 plate appearances, and stats only go back as far as 1974), who posted a .108 mark in 1995.

When you factor in Dunn’s contract — a four-year $56 million deal inked last December — well, as Dunn himself might say, that ain’t good.

The lone slugger: Despite the league-wide dominance of pitching, one hitter, Toronto’s Jose Bautista, is taking aim at one of the once-hallowed benchmarks of offense — the 60-home run barrier. If you’ll remember, the 60-homer club had only two members, Babe Ruth and Roger Maris, until the four-year barrage at height of the steroids era (1998-2001), when three players – Mark McGwire, Sammy Sosa and Barry Bonds – topped the mark a total of sixtimes.

Bautista, who seemingly came out of nowhere to hit 54 homers in 2010 — the first 50-plus-homer season since 2007 — entered the break with 31 homers in the Blue Jays’ first 92 games, putting him on a pace for 55. So Bautista will need to get hot in the second half to get to 60.

For that matter, Bautista, with a.702 slugging percentage in the first half, could also make a run at being the first to top the .700 barrier since Bonds in 2004.