Minor leagues Baker was drafted in
2002 by the
Oakland Athletics in the 4th round of the amateur draft. He was mentioned several times in
Michael Lewis' 2003 book
Moneyball. In March 2007, Baker was traded to the
Florida Marlins for minor league first-baseman
Jason Stokes.
Florida Marlins Baker was called up to the majors on July 9, 2008, after
Matt Treanor went on the disabled list. His first major league hit was a solo
home run off
Chan Ho Park of the
Los Angeles Dodgers on July 10. In 2009 to 2010 Baker platooned with teammate
Ronny Paulino; Baker played against right-handed pitchers while Paulino played against left-handed pitchers. Baker went on the disabled list in May 2010 with a strained flexor tendon in his right arm. At the end of the 2010 season, he had
Tommy John surgery when the elbow did not improve. He spent most of 2011 rehabbing and rejoined the Marlins that September, serving primarily as a pinch hitter.
San Diego Padres On November 22, 2011, Baker was traded to the
San Diego Padres for
Wade LeBlanc. Baker served as backup to
Nick Hundley and
Yasmani Grandal in
2012, starting 52 games and batting .238 while throwing out 16% of base runners. In
2013, he began the year as the backup to Hundley. He started 12 games for the Padres in April and May, and then was optioned to the Triple-A
Tucson Padres when Grandal returned from his 50-game suspension. He was designated for assignment on June 10, 2013.
Los Angeles Dodgers On June 15, 2013, Baker was claimed off waivers by the
Los Angeles Dodgers he was then optioned to AAA
Albuquerque. He was outrighted off the 40 man roster on August 5. In 40 games with the Isotopes, he hit .203. He became a free agent on October 1.
Chicago Cubs On December 13, 2013, Baker signed a minor league deal with an invitation to spring training with the
Chicago Cubs. Baker won the backup catcher job out of spring training when
George Kottaras was released. On July 29, 2014, Baker
pitched a scoreless top of the 16th inning with a popout and double play, as the Cubs had exhausted their bullpen in a game against the
Colorado Rockies. In the bottom half of the inning, he walked from a full count, then reached third with the bases loaded and one out. He scored the winning run on a lineout by
Starlin Castro, earning him the
win in the longest game, by time, in Cubs history. Baker became the fourth position player to earn a win since 1968, and first since
Chris Davis did so in 2012. John is the only Cubs position player to ever be credited with a pitching win in the history of the franchise.
Seattle Mariners On January 29, 2015, Baker signed a minor league contract with the
Seattle Mariners. He was released on May 20, 2015. ==Coaching career==