Mariano Rivera of the New York Yankees tips his cap to the crowd as he takes the mound in the eighth inning of the Major League Baseball All-Star Game at Citi Field in Flushing, New York, USA, on Tuesday.  The baseball All-Star Week culminates with the annual mid-season match-up of the best of the American and National Leagues playing for home field advantage in October’s World Series. (EPA)

Reuters/New York

Tight division races and the potential for historic individual exploits could offer a rousing finish to a Major League Baseball (MLB) season being played under the cloud of a doping scandal.

The second half of the season began yesterday after a four-day All-Star break, though actually only about 40% of the gruelling 162-game campaign remains.

Among the season surprises, the Pittsburgh Pirates (56-37) have a chance to end their 20-year run of losing baseball with a bang, as they trail the St. Louis Cardinals by just one game in the competitive National League Central.

The Cleveland Indians (51-44), meanwhile, have become a factor in the American League Central just 1-1/2 games behind the defending league champion Detroit Tigers.

Detroit’s Miguel Cabrera is threatening to produce an unprecedented back-to-back Triple Crown season, one that could be blocked by record-chasing home run hitter Chris Davis of the Baltimore Orioles.

There is much to look forward to in the campaign, though the clock is rapidly ticking down on the resolution of a probe into the alleged procurement of performance-enhancing drugs that could involve some 20 major league players.

While the prospects of players being expelled during this season appears to be slim, MLB Commissioner Bud Selig and Players Association chief Michael Weiner gave clear indications that the Biogenesis doping investigation was coming to a head.

Hearings, appeals and arbitration were expected to delay possible action on big names like Alex Rodriguez, Ryan Braun, Nelson Cruz and Bartolo Colon, who have all been implicated in the probe, unless settlements are agreed to by players found to have violated the game’s anti-doping rules.

On-field action will resume with full force Friday with all 30 teams scheduled to play, competition heating up and power hitters Cabrera and Davis getting back in the swing of things.

Last year Cabrera became the first player in 45 years to win the Triple Crown by sweeping the home run, runs batted in and batting average crowns. The Tigers third baseman is on an even faster pace with 30 homers, 95 RBIs and a .365 batting average.

But he trails Davis, 27, by seven home runs as the Orioles first baseman tries to stay on track for an assault on the American League record of 61 home runs by Roger Maris in 1961.

Supremacy of all six divisions could come down to the last games of September with the AL East and NL West looking like the hardest races to handicap.

The Boston Red Sox (58-39), who lost 93 games last year, lead the AL East by 2-1/2 games over the Tampa Bay Rays, with the Baltimore Orioles a further two games back and the injury-hit New York Yankees just six off the pace.

The Yankees have been getting great pitching but have been anemic at the plate, while they await the 2013 debuts of shortstop Derek Jeter (broken ankle) and slugging third baseman Rodriguez (hip surgery), who are both expected back soon.

Nearly as tight is the NL West with four teams within 6-1/2 games, although the first-place Arizona Diamondbacks (50-45) would trail all four AL East top contenders.

Revived by the sensational splash made by Cuban rookie Yasiel Puig, the big-spending Los Angeles Dodgers have climbed within 2-1/2 games of Arizona, with Colorado following two games ahead of World Series champions San Francisco Giants.

They are 23-15 in games played by Puig since he arrived in early June, including six-game and five-game winning streaks.

Last weekend’s no-hitter by Tim Lincecum could be a sign that the Giants are waking up, though the pitching-rich team needs a revival by Matt Cain and Barry Zito.