From Willits' view, Shields looks close to prime-time form. The Angels' setup man is eligible to come off the disabled list on Sunday, when the club is wrapping up a weekend series at home against the Rangers.
"The ball was jumping out of his hand," Willits said. "I didn't expect him to look that good, honestly. His breaking ball had good life, and everything had good movement. He looked like he was full-tilt out there to me."
Shields is on his way to Las Vegas to pitch for the Angels' Triple-A Salt Lake club on Thursday. Angels manager Mike Sciosica said that his durable reliever will be evaluated at that time and could be on his way back to Anaheim if all goes well.
"We're real excited," Scioscia said. "He threw the ball very well today; he had a great workout. It's a possibility he'll only need one game to get ready."
Before throwing to Willits and Robb Quinlan on Tuesday, Shields had delivered two impressive side sessions.
"Health-wise, that's not an issue anymore," Shields said. "I'm healthy. The training staff did a great job; they caught it quick.
"I was pleased with what went down today. In the beginning, I was a little erratic, but I was able to throw breaking balls, and they were sharp, and as the game -- or whatever it was -- went on, I started feeling the fastball more."
He got a late start this spring after experiencing some shoulder pain, and the forearm turned up stiff after a Cactus League effort, shutting him down again for two weeks.
An adjustment was made in Shields' mechanics by pitching coach Mike Butcher during one long-toss exercise, as Shields began reconditioning his arm in Arizona. He was making a movement with his left leg mid-delivery that impacted his upper body.
"Everything seems in sync now," Shields said. "No more karate kicks for me."
Butcher was encouraged by what he saw from Shields on Tuesday.
"He threw everything -- fastball, curveball, changeup," Butcher said. "He feels no pain, feels strong. He's not a guy we need to stretch out, so that's not an issue.
"There's a comfort zone he needs to find out there, and he's got to be honest with himself and the team. We'll rely on our guys watching him [in Las Vegas], as well."
Shields, who had a great first half in 2007, but struggled in the second half, is a weapon that few clubs can match. The American League leader or co-leader in holds, with 31 each in the past two seasons, he has pitched more innings over the past four seasons than any reliever in the Majors.
Lyle Spencer is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.