PHOENIX -- With Shaun Marcum on the comeback trail after starting Spring Training with a stiff shoulder, Marco Estrada may begin to shift his focus from stretching out as a starter to preparing for a bullpen role with the Brewers.

Marcum pitched three innings against the Dodgers in his Cactus League debut on Sunday. The right-hander is expected to throw 60 pitches in a Minor League his next time out, putting him on pace to be on the bubble as far as arm stamina by Opening Day, when a starting pitcher is ideally good for at least 75 pitches or five innings, but preferably more.

"If we think Marcum is ready, we will not be stretching Marco," manager Ron Roenicke said on Tuesday. "He's already to the point where his next outing he can be at 90 pitches. He's stretched out."

Estrada is 2-2 in six games this spring and has posted a 4.50 ERA in 15 innings. If Marcum starts the season in the rotation, Estrada will be prepared for spot starts should the need arise, with the Brewers confident he'd be able to give them four innings to get through a game.

"When he gets in a starting mode he mixes up locations really well," Roenicke said. "He's pitched better for us as a starter than he has as a reliever, though I like him as a reliever.

"We want him to get back in a mode where we're going to use him two, three innings, maybe one inning. He needs to pitch more often to try and get ready for our bullpen."

The Brewers are keeping their options open by starting Marcum in a Triple-A game Sunday, enabling them to backdate his appearance on the disabled list if they decide he needs more time before joining the rotation.

"Shaun was fine, he understands," Roenicke said, noting that no red flags have gone up regarding Marcum. "In case we want to give him an extra start [in the Minors once the season starts], we can do it."

Aoki sits against Royals with tight hamstring

PHOENIX -- Brewers outfielder Norichika Aoki was scratched from Tuesday's tilt with the Royals after coming in with a tight right hamstring.

The hamstring issue came up when Aoki pinch-hit in the ninth inning of Monday's game against the Indians. He delivered a game-winning RBI triple in the Brewers' 6-5 victory.

"He felt it -- it's not a strain, but it's there," manager Ron Roenicke said. "It's not worth putting him out there [Tuesday]. He's got a lot of at-bats. To give him a day off is no big deal."

Aoki looks like the fourth outfielder on the club, but with Cory Hart questionable for the start of the season as he recovers from knee surgery, Aoki has a good shot at being in the Opening Day lineup. He's hit .327 (16-for-49) with three triples, a homer, eight RBIs and three steals this spring.

"We'll see how he is [Wednesday], and if it's gone, we'll try to get him back in," Roenicke said.

Caleb Gindl started in right in place of Aoki on Tuesday.

Gallardo hopeful for Opening Day assignment

PHOENIX -- Yovani Gallardo suffered a hiccup on the mound on Tuesday, losing his timing for an inning in the Brewers' 9-7 loss to the Royals. But the right-hander remains on schedule for a possible Opening Day assignment when his turn comes around again in 10 days.

"He was a little out of whack," manager Ron Roenicke said. "Pitches were either up in the zone, or he'd spike a breaking ball down. He couldn't find that in-between. Hopefully, he remembers what he did to get out of it and get back on line."

Gallardo lost his rhythm in a three-run third frame, midway through a five-inning, four-run outing, but he was able to recognize what was wrong and make critical adjustments, retiring the final seven batters he faced.

"I started staying back a little bit," Gallardo said. "Staying over the rubber a little longer and getting to that balance point before going to home plate, instead of trying to do it all at once. In the third inning, I was jumping a little too quick. Those last two innings, that's my normal rhythm. It's a good thing to be able to find it. The ball was coming out a lot easier, and my offspeed stuff was sharper and late."

Gallardo made good use of his changeup, keeping hitters off-balance and striking out six. He deemed himself ready for the regular season, and noted that he's ready to get going also after one more tune-up on Sunday against the Giants.

"It's always good to get the bad ones out of the way," Gallardo said. "That final week of Spring Training is always the toughest one. You're excited, anxious, nervous, waiting for Opening day. You just want to get it under way."

If the schedule holds up, Gallardo is in position to throw the first pitch when the Crew faces the World Series champion Cardinals in the season opener at home on April 6. Roenicke expects to make an official announcement Wednesday morning, and Gallardo was emphatic that nothing was set until the manager gets the pitching staff together and tells them. But Gallardo was hopeful that the calendar and the math are on his side.

"It would mean a lot [to get the start]," Gallardo said. "It shows you what they think of you, especially having that opportunity to hopefully do it three years in a row. It's an exciting game. You want to start the right way. The whole atmosphere of Opening Day, it's a little bit more exciting, nervous, than regular season games. Knowing we fell a couple games short playing against the Cardinals last year, it just adds to it a little more."

Perez returns to mound after hospital stay

PHOENIX -- Reliever Juan Perez was back on the mound Monday for the first time since a short hospital stay for a collapsed lung two weeks ago.

"He threw a bullpen [Monday] -- it went real well, and he's accelerating fast," manager Ron Roenicke said. "He had a smile on his face and he felt good."

Perez, 33, has played in parts of three seasons for the Pirates and Phillies, going 1-1 with a 4.79 ERA in 32 relief appearances. The left-hander was a non-roster invitee to Spring Training and pitched well enough early on to gain serious consideration for the bullpen, yielding zero runs and two hits while striking out two over the course of three appearances and 3 1/3 innings.

"I think he probably will be ready [to pitch in a game before the Brewers break camp], but I don't know that he will," Roenicke said.

Perez is expected to throw another side session on Thursday, and Roenicke said it was "to be determined" if he still had a chance at making the 25-man roster for Opening Day.

"We're OK with where he is in his status, because he's on a Minor League deal," Roenicke said, meaning the Brewers don't need to worry about keeping him out of Cactus League games in order to backdate a trip to the disabled list to start the season.

Last call

• Shortstop Alex Gonzalez was back in the Brewers' lineup on Tuesday after sitting out Monday's game against the Indians with a bruised heel. He iced it down Monday and said he felt fine Tuesday.

Gonzalez hit a two-run homer in the seventh inning and went 1-for-3 in the Brewers' 9-6 loss to Kansas City.

• Corey Hart appears to remain on track to make a Minor League appearance on Wednesday. It would be his first game action of the Cactus League season.

"Everything went well [Monday]," Roenicke said of Hart's activities. "[Tuesday] he's sliding and he's running the bases again."

• Outfielder Carlos Gomez remained out of the lineup on Tuesday with an illness.

"I was hoping Gomez would be with us [Tuesday]," Roenicke said." Gomez is going to get some at bats in the Minors. Just hit. We won't hit him that much, but it's just getting him back in the flow again, instead of putting him back out there in the outfield and having him run around."