Boston Red Sox Brentz was drafted by the
Boston Red Sox in the first round of the
2010 Major League Baseball draft. Entering 2013, Brentz was ranked as the sixth best prospect in the Red Sox minor league system. He was preparing to participate in
spring training of 2013 until he accidentally shot himself in the leg while cleaning his handgun during the offseason. Brentz returned to the
Pawtucket Red Sox of the
Triple-A International League, but missed time in July and August due to a
torn meniscus. He posted a .262 average with 19 home runs and 64 RBI in 88 games between Pawtucket and the Gulf Coast Red Sox, where he completed a rehab assignment, while tying with David Chester for the most home runs in the system. Brentz was added to the Red Sox'
40-man roster on November 20, 2013, in order to be protected from the
Rule 5 draft. He played for Pawtucket in 2014 and was part of the team that won the
International League Governors' Cup. After Pawtucket lost the one-game
Triple-A World Series to the
Omaha Storm Chasers of the
Pacific Coast League, the Red Sox promoted Brentz to the major leagues, and he made his major league debut on September 17. He recorded a double off
Pittsburgh Pirates pitcher
Francisco Liriano in his first game for his initial Major League hit. In 2015, Brentz missed time from May 20 through August 2 with a right hamstring strain. In 54 games with Pawtucket and 12 games of rehab for the
Portland Sea Dogs, he hit a combined .242 with five home runs and 24 RBI. He also had a stint with the Red Sox that year, hitting .279 with one home run and seven RBI in 25 games. Brentz hit his first MLB home run on June 26, 2016, off Rangers pitcher
Martin Pérez. On March 31, 2017, Brentz was outrighted off Boston's 40-man roster and accepted the assignment to Pawtucket. He is out of options. He was named International League Player of the Week for the week of June 18. He was also named an IL Mid-Season All-Star and a
Triple-A Home Run Derby participant. Brentz, who hit a total of 38 home runs in the derby, defeated
Daniel Vogelbach in the final round to win the derby title. On November 2, Brentz had his contract purchased from Triple-A.
New York Mets On February 20, 2018, Brentz was traded to the
Pittsburgh Pirates in exchange for cash considerations. He was placed on outright waivers on March 24. He did not play for the Pirates organization, as on March 26, he was claimed off waivers by the
New York Mets, and was outrighted to Triple-A on March 28. Overall during 2018, Brentz batted .263 in 57 minor league games.
Boston Red Sox (second stint) On December 23, 2018, Brentz signed a minor league deal to return to the
Boston Red Sox, and was assigned to the Triple–A
Pawtucket Red Sox. Brentz elected free agency following the season on November 4, 2019.
Somerset Patriots On January 31, 2020, Brentz signed with the
Somerset Patriots of the
Atlantic League of Professional Baseball. He did not play a game for the team due to the cancellation of the ALPB season because of the
COVID-19 pandemic and became a free agent after the season.
Kane County Cougars On November 17, 2021, Brentz signed with the
Kane County Cougars of the
American Association of Professional Baseball. Brentz played 7 games for the Cougars, during which he hit .222 with one home run and one RBI. On July 31, 2022, Brentz was released by the Cougars. ==Coaching career==