In 2007, he attended Baker University and played college baseball for the Baker Wildcats of the National Association of Intercollegiate Athletics. He transferred to the University of Arkansas in 2008 but did not play baseball for the Razorbacks. Instead, he served as a backup catcher on their team that won the 2009 College World Series. Blake Treinen's career batting average is.292 with 155 hits, 39 doubles, 10 triples, and 21 home runs. He has scored 92 times and has been caught 89 times. In 2009, he finished with 91 walks vs. only 67 strikeouts. Treinen was drafted by the Oakland A's in the eighth round of the 2010 MLB Draft. He chose to accept an offer from the Washington Nationals instead, signing for $300,000 just below the maximum amount allowable. He made his major league debut on August 25, 2015. The A's lost 1-0 to the Seattle Mariners that day. During Game 3 of the 2016 National League Division Series between the Los Angeles Dodgers and Arizona Diamondbacks, Treinen came out of retirement to replace Yasmani Grandal (who had been traded to the Dodgers earlier in the day) as the starting catcher for the Dodgers. He caught Matt Kemp during that game and Games 4 and 5 as well.