Sweeney was scratched about 45 minutes before the start of Saturday's game. The team didn't immediately announce why, but Sweeney has struggled with back spasms this year and primarily is a designated hitter. He played the field Friday night and went 2 for 4 with an RBI.
The Mariners were aware of Aardsma's plan to fly home to join his wife, Andrea, for the birth of their child. The club expects him to be gone three days. Seattle manager Don Wakamatsu said Brandon League will be the interim closer in Aardsma's absence.
League has three saves in his major league career. His last was May 11 at Baltimore.