NEW YORK -- Masahiro Tanaka has a strained right hamstring and won't make his scheduled start for the New York Yankees this week during a crucial series in Toronto.

The right-hander got hurt running to first base after bunting Friday in an interleague game against the Mets at Citi Field. He pitched another five innings - pretty well, too - but an MRI on Saturday revealed the strain.

It is a considerable blow to the Yankees, who hope Tanaka will miss only one turn. They juggled their rotation specifically so he could face the Blue Jays, who held a three-game lead in the AL East over New York going into Sunday night's Subway Series finale.

Struggling right-hander Ivan Nova, recently removed from the rotation, will start in Tanaka's place Wednesday night.

Tanaka has been the team's best starter lately. He is 12-7 with a 3.38 ERA, including 2-0 with a 0.56 ERA in his last two starts against Toronto.