BALTIMORE — The Baltimore Orioles were masters of seduction on Wednesday night. They patiently watched first pitch after first pitch from Masahiro Tanaka, perhaps giving him the idea that he could steal a strike.

Then, when Tanaka most needed to jump ahead in the count, the Orioles pounced. Adam Jones hit a three-run homer and a run-scoring double, and Mark Trumbo hit a two-run double that fooled right fielder Aaron Judge — all on rare first-pitch swings against Tanaka. Those hits doomed the Yankees in a 10-4 defeat.

The Yankees’ lead in the American League East was reduced to two games over Boston as they headed to Toronto, which is getting hot and healthy after a dreadful start. But most disconcerting for the Yankees was the performance of Tanaka.

They hoped a 13-strikeout performance in his last start, against Oakland, was a sign that he was righting his recent slide. But he allowed at least six runs for the third time in four starts, raising his E.R.A. even more, to 6.34. He allowed 11 home runs in May.