BOSTON (Reuters) - The American League-leading Boston Red Sox have placed starting pitcher Clay Buchholz on the 15-day disabled list because of lower back strain, the Major League Baseball team said on Sunday.

Buchholz, who is coming off a career-best 17-7 record in 2010, is 6-3 with a 3.48 earned run average this season.

During his last start, the 26-year-old Buchholz allowed one run and two hits in five innings before leaving Thursday's game because of lower back tightness.

The Red Sox said in a statement left-handed pitcher Andrew Miller from Triple-A Pawtucket was added to the roster and he is scheduled to pitch Monday against the San Diego Padres.

(Reporting by Frank Pingue in Toronto; Editing by Mark Lamport-Stokes)