A California native, Arnerich attended college in Texas. After his junior year, he signed with the Kansas City Royals and played for minor league baseball teams in Iowa, Delaware, and Kansas from 2001 to 2004. Arnerich then joined the Florida Marlins and played minor league in North Carolina and Florida in 2004 and 2005.
Returning to California, Arnerich began coaching college teams in 2006 and earned a bachelor's degree in 2008. He coached a collegiate summer team in Minnesota from 2007 to 2009. Arnerich joined the Mariners in 2014, and was named a hitting coach in 2022. In 2024, he became the team's bullpen coach, replacing Stephen Vogt.[1]
Arnerich became an assistant coach in 2006 at Sonoma State University,[2] where he earned a Bachelor of Science degree in Sociology in 2008.[8][9] He coached for the St. Cloud River Bats summer team from 2007 to 2009,[9] and the California Golden Bears from 2007 to 2014, during which the team went to the College World Series in 2011. In 2014, he joined the Seattle Mariners organization,[8] as a hitting and catching coordinator beginning in 2017.[10] The Mariners promoted Arnerich to minor league field coordinator in 2020,[8] major league hitting coach for the 2022 season,[11] and bullpen coach in 2024.[1]
Personal life
Arnerich has coarctation of the aorta, a narrowing of the artery from the heart. He received a mechanical valve in 2012, but developed a staph infection near the device in 2013. In October 2013, his doctors said a second surgery to replace the valve was necessary, with only a 50/50 chance of his surviving it. A later CT scan showed the infection had cleared, however, and Arnerich returned to work in January 2014.[12]
During a COVID-19 pandemic lockdown in spring 2020, Arnerich joined other Mariners players in posting video drills to encourage kids to continue in baseball activity. Arnerich's fielding drill video included his young son and daughter.[13][14]