TEMPE, Ariz. -- Kelvim Escobar took another sure, steady stride on Sunday toward returning to the Angels' rotation.

With Angels pitching coach Mike Butcher watching intently, the veteran right-hander cleared another big hurdle with relative ease. Throwing his first full bullpen session -- he'd delivered 25 pitches at a distance of 55 feet earlier in the spring -- since October 2007, Escobar unleashed 25 fastballs in natural form, leading to speculation he could return to game action sooner than originally thought.

Butcher was as delighted as the pitcher with the latest evidence of his remarkable recovery from right shoulder surgery last July. Escobar tweaked his left calf doing exercises a week ago, but there was no residual pain, and he was free and easy with his delivery.

"He was outstanding," Butcher said. "The ball came out of his hand real well. He threw all fastballs, and the ball was located well down in the zone. No complaints at all. He looks very natural out there.

"You can tell when he's confident by his facial expression, the way he's talking. It was there. It's one step at a time, but he definitely came into camp in tremendous shape, and that helps. He's a guy you never have to push. He's always pushing himself."

That brings us to the one concern: keeping Escobar from trying to do too much too soon. He is being closely monitored by manager Mike Scioscia, Butcher and the medical staff on a daily basis.

The early prognosis was a return around the July All-Star break. It is now possible he'll be back on the mound in a Major League game sometime in May.

"The early indications were somewhere around midseason," Scioscia said. "Whether it's May 15, June 1, we can't throw dates out there. We don't know. It's obvious he's going to be at the front end of that window they gave us after surgery."