OAKLAND, Calif. (AP) Athletics right-hander Daniel Mengden had right foot surgery Wednesday in Houston after breaking a bone during a bullpen session at home Jan. 31.

He is expected to wear a walking boot for six weeks and a return date is not known.

The team said Wednesday he fractured the medial tibial sesamoid bone, and the surgery was performed by Dr. Kevin Varner. Mengden had been set to compete for the club's fifth starter spot in spring training beginning next week in Mesa, Arizona.

Mengden was 2-9 in 14 starts last season for Oakland. He made his major league debut having never pitched higher than Class A ball. Overall between the A's, Double-A and Triple-A last season, he was 10-2 with a 1.46 ERA and .197 opponents' batting average over 17 starts.