Hayes served as the bullpen catcher for the San Francisco Giants from 2003 to 2014, winning three World Series Championships (2010, 2012, 2014). In December 2014, he was promoted to first base coach for the 2015 season. He was removed as first base coach by the Giants after the 2016 season, but remained on the staff in a non-coaching role. After serving as the Giants' minor league catching coordinator in 2018, Hayes returned as manager of the San Jose Giants in 2019, but resigned mid-season.