PHOENIX -- Padres starting pitcher Shawn Estes' broken bone has healed, but the left-hander has encountered a new problem in his pitching hand.

Attempting to return from the disabled list after fracturing his thumb May 30, Estes has an infection underneath one of his fingernails that is causing a bit of discomfort.

Estes has pitched in two rehab starts for Triple-A Portland, most recently Tuesday night in Tucson, when he allowed four runs on nine hits in four innings.

The 35-year-old originally fractured his thumb while slipping down the clubhouse stairs that lead to the visiting dugout at AT&T Park in San Francisco.

Manager Bud Black said Estes' next start, which would have been Sunday, has been pushed back two days.

"When he throws, his index finger hits it," Black said. "It's sort of a freakish thing."

Estes made just five appearances for the Padres this season, four of them starts, going 1-1 with a 3.33 ERA.