Updated

Oakland Athletics pitcher Brett Anderson won't return to action for at least another month.

The club revealed on Friday that the 25-year-old was diagnosed with a navicular stress fracture in his right foot after undergoing CT and bone scans on Thursday which revealed the damage.

He will be re-evaluated in four weeks.

Anderson had been placed on the 15-day disabled list on May 1 with a sprained right ankle initially suffered during an April 19 start against Tampa Bay. He has gone 1-4 with a 6.21 earned run average in six games (five starts) this season.