A changing of the guard at 3B

Oakland's Josh Donaldson leads MLB third basemen in WAR this season, with 3.5. Kyle Terada/USA TODAY Sports

Baseball is full of new stars. At 22 years old, Mike Trout has already established himself as the best player in the game. Yasiel Puig and Bryce Harper draw as much attention from everything they say and do off the field as they do from their spectacular plays on it. And while injuries have put the emerging stardom of pitchers such as Matt Harvey and Jose Fernandez on hold, Masahiro Tanaka, Garrett Richards and others have burst onto the scene.

Coming into the season, the one position that seemed to be safely led by its veteran stars was third base. Since Evan Longoria made his debut for the Tampa Bay Rays in 2008, he, Adrian Beltre, David Wright and Ryan Zimmerman have been a consistent presence atop the third-base leaderboards. Many of their contemporaries have since moved off the position, such as Miguel Cabrera, Jose Bautista, and Alex Gordon. Others have retired or are otherwise out of baseball, such as Chipper Jones, Scott Rolen and Alex Rodriguez. Potential new stars such as Chase Headley and Pablo Sandoval have enjoyed great seasons in the interim, but none have been able to sustain an elite level of play. So entering 2014, it seemed a given that Longoria, Beltre, Wright and Zimmerman would once again be the class of the position.

Midway through the season, that has not been the case. Longoria is having the worst offensive season of his career. His .726 OPS is 116 points lower than his previous career low from 2013. In addition, this is his worst defensive season. He has cost the Rays four runs with his defense, according to defensive runs saved (DRS), which has him on pace for the first below-average defensive season of his career. Beltre continues to hit, but after saving 170 runs with his defense from 2003-2012, the most in baseball in that time, he has cost the Rangers four runs since the start of 2013. At 35 years old, Beltre may have begun to decline. Wright is fighting through a shoulder injury and is on pace for the fewest steals of his career and fewest home runs since 2009. Meanwhile, persistent shoulder injuries had the Nationals experimenting with Zimmerman in left field, which may eventually become his new position long-term.

All of a sudden, the third-base leaderboards are looking a lot different. None of the four mainstays at the position are in the top five in wins above replacement (WAR), a statistic that comprehensively measures a player's overall offensive and defensive value. Instead, the leaders include several established players who have reached a new level of success in 2014 and a couple of players who have moved to third from the middle infield.