The San Francisco Giants placed pitcher Jeremy Affeldt on the 15-day disabled list Tuesday with a right knee sprain.

Affeldt has made 10 relief appearances for the Giants this season, allowing nine runs -- five earned -- on 15 hits in 11 innings.

In a corresponding roster move, the Giants purchased the contract of fellow left-hander Travis Blackley from Triple-A Fresno.

Blackley hasn't pitched in the majors since making two starts for San Francisco in 2007. He was having a solid season for Fresno at the time of his promotion, compiling a 3-0 record with a 0.39 ERA.

To make room for Blackley on the 40-man roster, the Giants designated outfielder Tyler Graham for assignment.