Hammel had a successful bullpen session in Toronto on Tuesday. He hasn't appeared in a major league game since July 13, when he left a start against Detroit with pain in his right knee. He underwent surgery the following week.
Hammel pitched five scoreless innings in a rehab start at Class A Frederick last Saturday, his first live action following a pair of simulated games. The Orioles wanted to see how Hammel performed in his bullpen session before deciding whether to start him against the Yankees.
Right-hander Chris Tillman, who left Sunday's victory over the Yankees with a sore elbow, had an MRI Tuesday. Manager Buck Showalter said Tillman has no structural damage, just minor inflammation.
Tillman will work out at Double-A Bowie until Baltimore returns home. It's not yet known when he will pitch again, but he could face the Yankees this weekend.
Infielder Jim Thome, out since July 28 with a herniated disk in his neck, is feeling better and is scheduled to see a doctor on Thursday, Showalter said. Left-hander Troy Patton, sidelined since Aug. 13 by a sprained right ankle, threw from 120 feet on flat ground Tuesday, up from 90 feet the day before.
Hammel will fly home ahead of his teammates before Wednesday's series finale against the Blue Jays, avoiding a late-night return to Baltimore. Showalter said Hammel will be on a pitch count against New York, but would not specify how long he would be able to go.
Hammel's start pushes Wei-Yin Chen back to Friday, giving the Taiwanese rookie an extra day of rest.
Also Tuesday, the Orioles recalled left-hander Zach Britton from Triple-A Norfolk.