Acquired Saturday in a trade that sent two minor leaguers to Philadelphia, Thome hurriedly traveled from Miami to Baltimore and was in the starting lineup against Cleveland.
The 41-year-old slugger was delighted to join an American League team in contention to make the postseason. Baltimore entered Sunday's game with a 42-35 record and in second place in the AL East.
Playing in the AL means Thome can play more often as a designated hitter. He expected to play more first base with the Phillies, but wasn't physically capable of doing so.
He said: "That put them in a tough situation and I understood that."