Oakland Athletics players celebrate after Matt Olson, center left, hit a grand slam home run against the Los Angeles Angels in the tenth inning a baseball game in Oakland, Calif., Friday, July 24, 2020.
According to STATS, Olson became the third player to hit a walkoff grand slam on opening day.
The game went to the 10th tied at 3 after Jason Castros tying homer in the ninth against As closer Liam Hendriks.
The Angels didn't deliver a win for Maddon in his Angels managerial debut.
UP NEXTLHP Sean Manaea, who went 4-0 last season in September after returning from shoulder surgery before losing the wild card game, pitches Saturday opposite Angels RHP Dylan Bundy.