He played in Major League Baseball (MLB) for the Seattle Mariners, Boston Red Sox and Texas Rangers.

His 2007 season with the Binghamton Mets of the Double-A Eastern League would be somewhat derailed by a broken finger, which he felt affected his swing even after returning from the disabled list.

[2] Carp enjoyed a great bounceback season in 2008, setting career highs in average, on-base percentage, OPS, doubles, homers, and walks.

[3] He made his major league debut with the Mariners on June 17, 2009, pinch-hitting in a game against the San Diego Padres and drawing a walk.

Carp was named the American League Rookie of the Month in August,[5] during which he had a 20-game hitting streak, batting .313 and driving in 25 runs.

[7] On June 4, 2013, Carp earned his first career ejection for arguing a strike three call made by umpire Andy Fletcher.

[8] On September 11, 2013, Carp hit a go-ahead grand slam to dead center off pitcher Roberto Hernandez of the Tampa Bay Rays to put ahead the Red Sox and eventually win the game in the 10th inning.

On April 24, 2014, in the ninth inning against the Yankees at Fenway Park, Carp appeared as a relief pitcher after the Red Sox had used all their relievers.

The request made news after the Red Sox traded veteran pitcher Jake Peavy to the San Francisco Giants on July 26.