Pujols, a bench coach at the start of the season, made his major league managerial debut Tuesday when the Tigers hosted the Chicago White Sox.
Pujols managed the Tigers' Class AA affiliate in Erie to the Eastern League's Southern Division title last year. He also served as a coach on the World Team at last summer's Futures Game in Seattle.
Pujols spent the previous eight seasons as a coach under Felipe Alou with the Montreal Expos and six more in the club's farm system working with Dave Dombrowski, the team president.
The Tigers also revamped their coaching staff Tuesday, naming Steve McCatty pitching coach, Jeff Jones bullpen coach and Rafael Landestoy infield/first base coach. All three were promoted from minor league assignments.
Third base coach Doug Mansolino and former pitching coach Dan Warthen were fired. Juan Samuel was named third base coach and will continue in his capacity as an outfield coach.
An 0-6 start cost Garner and General Manager Randy Smith their jobs. Dombrowski assumed the additional role of general manager.