Chris Carpenter returned from Dallas on Thursday afternoon. Friday he returned to a bullpen mound for the first time since experiencing a temporary setback in his recovery from nerve-related shoulder weakness.

Carpenter threw for about 10 minutes from a bullpen mound in 102-degree heat, marking his first activity since interrupting his rehab to pursue a second opinion from a Dallas specialist. Carpenter, who was within five days of beginning a minor-league rehab assignment when confronted by renewed weakness last Sunday in Kansas City, said Friday he believes himself back on course.

"I think they have a little better feel of what's going on and I think the trip to Dallas was worthwhile," Carpenter said after his bullpen session.

Thursday's examination lasted less than an hour and confirmed a prior diagnosis that he is suffering thoracic outlet syndrome, a condition that affects nerves that traverse from the neck area to the shoulder into the upper arm.

Though all parties sidestepped talk of a modified timetable following Friday's session, Carpenter recognizes that he is throwing against the clock.

General manager John Mozeliak suggested surgery could be in Carpenter's future. Surgery was presented — and rejected — as an option in 2008.