Athletics' Daniel Mengden: Undergoes foot surgery

Mengden underwent right foot surgery after fracturing a bone during a bullpen session, Susan Slusser of The San Fransisco Chronicle reports.

Mengden, who was competing for the fifth spot in the rotation, will be in a walking boot for six weeks and there is no timetable for his return to action. The right-hander finished his rookie season 2-9 with a 6.50 ERA, but showed signs of improvement as the year progressed. Mengden's injury means Andrew Triggs will likely be the fifth starter for Oakland.