BOSTON — Mookie Betts hit three home runs against James Paxton on Friday night during the first four innings of a 10-5 blowout of the Yankees, whose starting pitchers have stumbled this week in historic fashion.

Betts first homered on Paxton’s eighth pitch in a three-run first inning that included a two-run homer by J. D. Martinez. Betts went deep again leading off the third for a 4-0 lead and then hit a two-run drive in the fourth for a 7-0 advantage.

Betts added a run-scoring double in the sixth off David Hale to give him five R.B.I., and he grounded out in the eighth. With his fifth career three-homer game, Betts raised his season total to 18 homers.

Batters have had three-homer games on four straight days for the first time in big league history. Betts followed the Mets’ Robinson Cano, St. Louis’s Paul DeJong and Minnesota’s Nelson Cruz.