"I was running better and feeling better than I have in a long time, probably since 2007," Willits said. "This is the first time I've ever hurt that one. It came out of the blue.
"It kind of cramped up on me, and then I felt it pretty good when I hit third base on my way to scoring [on Sunday against the Cubs]. I kind of coasted home and had to come out of the game."
If he continues to improve, Willits should be back on the field "by early next week," manager Mike Scioscia said. The versatile switch-hitter is hoping to nail down the backup spot in the outfield vacated by Gary Matthews Jr., dealt to the Mets for reliever Brian Stokes.
"He's got to do some progressives running the bases, making cuts," Scioscia said.
Willits was able to work out over the offseason for the first time since the winter preceding his breakout 2007 season, when he was a pivotal factor in the Angels' American League West title drive and finished fifth in the AL Rookie of the Year balloting.
"I had the gallbladder surgery after the '07 season, and I tore my oblique in '08 and wasn't able to do much of anything that winter," Willits said. "This winter I changed my workouts and went from doing heavy weights to lighter weights and more reps. I did a ton of yoga and a lot more cardio to get down to 181, 182 [pounds].
"I was never below 185 before. Five or six pounds might not sound like much, but it's like running with a five-pound weight in your hand. I feel quicker, faster this spring. I think that can help me on the bases and in the field. I kind of feel like I did before all this stuff started happening to me."
He also feels the difference in his weight shift at the plate, getting his lower body into his swing at the suggestion of hitting coach Mickey Hatcher.
Willits is not trying to turn into Kendry Morales, launching balls over walls, but he does think he can drive balls into gaps and keep pitchers from grooving first-pitch fastballs.
"Hatch has been on me to use my back side to drive it into the gaps," Willits said. "I was starting to feel myself getting into balls before I tweaked the hamstring. On the [RBI] base hit that day [against the Cubs], I really felt my back side get into it.
"I'm still a disciplined hitter. But if they're going to throw the first two pitches right over the plate, I've got to be aggressive. I have to create in pitchers' minds that they have to make better pitches, and that's when I can work counts.
"I like to see a lot of pitches to get locked in. I need eight-pitch at-bats when I foul off a lot of pitches. I'm that kind of hitter, and I can't change. But I can help myself get in those deep counts by showing I can drive pitches to the gaps."
In 2007, Willits set club records for rookies with his .293 batting average and .391 on-base percentage. His 20 doubles in 430 at-bats showed that he was on occasion hitting the gaps. He had 27 steals in 35 attempts and twice has stolen at least 40 bases in Minor League seasons.
"The last few years have been frustrating," Willits said, having had a total of only 228 plate appearances in '08 and '09. "But I'm confident I can get back to being the kind of player I was in '07. I'm really looking forward to getting back on the field."
As Opening Day approaches, the final two weeks of exhibition games will help Scioscia and his staff sort out the roster situation. Brandon Wood, Bobby Wilson and Terry Evans are out of Minor League options and must be kept on the 25-man roster or moved in a deal in order to avoid being exposed to the waiver wire.
Wood, his average climbing to .303 through Thursday with a steady string of line-drive hits, is making a strong case for the third-base job. Wilson is bidding to make it as a third catcher, while Evans is in the mix for an outfield role.
Lyle Spencer is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.