PHOENIX -- Brewers right-hander Braden Looper threw a bullpen session Wednesday for the first time since straining a muscle along his ribcage, and the team expects him to be in the starting rotation by Opening Day.

That came as some relief to manager Ken Macha, who was worried that he might have to go into the season with one of the team's top offseason pickups on the disabled list. Looper, who inked a one-year, $4.75 million deal last month, was lined up to start the Brewers' April 10 home opener against the Chicago Cubs before a setback on Feb. 28.

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Now it is increasingly likely that he will make that first regular-season start. Looper threw 42 pitches from a bullpen mound to catcher Mike Rivera, with pitching coach Bill Castro and assistant athletic trainer Dan Wright looking on.

"I felt really good," Looper said. "I was a little fatigued at the end, but that's going to happen when I've only played catch for a few days. I feel healthy, and everything was down [in the strike zone]. That's a good sign, being able to pull the ball down."

Looper said that he worked at about 90 percent of full strength on Tuesday. He also said that since converting from a late-inning reliever to a starting pitcher in 2007, he has learned to pitch at about 95 percent of full intensity and focus more on location than velocity.

Looper pitched in an intrasquad game Feb. 24, but he was scratched minutes before his Cactus League debut with tightness at the back of his left ribcage. Because such oblique injuries can linger, Brewers medical staffers suggested a very conservative approach.

Looper admits he wanted to push things along. But since the current plan left him ready to pitch at the start of the season, he went with it.

"I felt like it could have been more aggressive, but as long as I'm still on schedule [for the season], I'm good," Looper said. "I told you guys from the first time that I couldn't fathom starting the season on the DL. As long as I stay on this course ... I'm sure I'll be ready for it."

Looper will be re-evaluated on Thursday and could pitch again on Friday, either in the bullpen again or on a field against hitters. He still has several steps in front of him before appearing in a Cactus League contest, and he might have to make his first game appearance in Minor League camp, because it falls on a day Dave Bush is scheduled to work in the "A" game .

That logjam will probably be eased after the team's March 24 off-day, when Macha is expected to give the other four starters an extra day off. Looper would pitch March 26 and 31 and then would remain in Arizona to pitch a Minor League game on April 5, when the Brewers are off before their April 7 season opener in San Francisco. Even with Looper making progress, Macha said he would continue to "stretch out" righty Seth McClung as a starter. With starters' innings increasing -- Bush was scheduled for four innings and 60 pitches against the White Sox on Wednesday -- the team is poised to make another round of roster cuts later this week.

"Guys that are going to start in Triple-A are probably going to have to go down there [to Minor League camp] and get stretched out," Macha said.

That would indicate candidates for what Macha called roster "trimming" could include some combination of right-hander Nick Green and/or left-handers Chase Wright, Chris Narveson, Sam Narron and Lindsay Gulin, all of whom could begin the year at Triple-A Nashville.

In other injury briefs:

• Bill Hall, sidelined since the start of camp by a torn left calf muscle, could debut in a game, "perhaps by the weekend," Macha said. Hall played catch and took batting practice on Wednesday.

• Rivera (right hamstring) caught Looper's bullpen session on Wednesday after running on the treadmill Tuesday. He continues to make progress and said he hoped to be playing in games by the end of next week.

• Catcher Angel Salome (back) hit off a tee and took part in "soft toss" on Wednesday, and he also handled Manny Parra's bullpen on Wednesday.

• Outfielder Tony Gwynn Jr. (right shoulder) played catch from 60 feet with head athletic trainer Roger Caplinger.