Billingsley to begin Triple-A rehab assignment

O'Sullivan gets Sunday start vs. Nationals

Billingsley to begin Triple-A rehab assignment

PHILADELPHIA -- The Phillies announced Thursday that Sean O'Sullivan will be their No. 5 starter and pitch Sunday against the Nationals.

They hope Chad Billingsley is not far behind.

Billingsley, 30, begins a rehab assignment Friday with Triple-A Lehigh Valley. He is recovering from a pair of right elbow surgeries that have limited him to just 12 innings in the big leagues since 2012. But everything has been going well lately, and there is a good chance he could join the Phillies rotation before the end of the month.

"I'm pretty excited going into tomorrow," Billingsley said. "Hopefully everything goes good."

The Phillies signed Billingsley to a one-year, $1.5 million contract in the offseason. It is filled with performance bonuses, and in a best-case scenario Billingsley returns to form and becomes an attractive trade chip in July.

Billingsley has built up his arm strength to about 45 pitches, so he could throw around 60 pitches Friday. He probably needs to build up to 100 pitches before he is ready to join the Phillies, which could mean three or four rehab starts.

Todd Zolecki is a reporter for MLB.com. Read his Phillies blog The Zo Zone. Follow him on Twitter. This story was not subject to the approval of Major League Baseball or its clubs.