JUPITER, Fla. -- There is more reason for optimism at Marlins camp.

As the team was facing the Astros in Kissimmee on Wednesday, a handful of key players participated in a Minor League game on a back field at the Roger Dean Stadium complex.

Outfielders Logan Morrison (right knee) and Giancarlo Stanton (left knee) each were used as a designated hitter. Both got a few at-bats, with each collecting hits against Mets Minor Leaguers.

Morrison laced a double to right-center, and he ran just fine to second base. Unlike previous times when he was used as a designated hitter, Morrison stayed on the bases, instead of yielding to a pinch-runner.

Stanton added a single.

The two are expected to play the field on Thursday, and the hope is they will be ready for the April 4 opener against the Cardinals at Marlins Park.

Also on Wednesday, Greg Dobbs (left hamstring) played third base, and he also took a few at-bats. Dobbs is also confident he will be ready for Opening Day.

Lefty specialist Randy Choate (right side muscle strain) tossed one inning, facing left-handed hitters. Choate was initially supposed to travel to Kissimmee, but the team kept him back to primarily face left-handed hitters.

Additionally, relievers Heath Bell and Steve Cishek each tossed an inning on a back field. Both are fine. They just were getting their work in as they look to fine tune for the start of the season.

Ceda will likely need Tommy John surgery

JUPITER, Fla. -- A week ago, Jose Ceda was putting himself in position to win a spot in the Marlins' bullpen.

Now, the right-hander is facing possible surgery.

Ceda has an elbow sprain, and he appears likely to have Tommy John surgery.

The Marlins obtained Ceda from the Cubs after the 2008 season for Kevin Gregg. He last pitched on March 22 against the Braves in Lake Buena Vista, Fla.

Ceda had eight strikeouts in 7 1/3 innings, and was putting himself in position to win a roster spot.

There are one or two openings in the bullpen, which is close to being set. Heath Bell will close, and Edward Mujica is getting the first shot at the eighth-inning role. Steve Cishek, Ryan Webb, Mike Dunn and Randy Choate are expected to be on the squad.

In the mix are non-roster invitee Chad Gaudin and lefty Wade LeBlanc, who has had an impressive camp. LeBlanc is the front-runner to be the choice if something were to happen to anyone in the rotation. He is a long-relief candidate.

Big Z recognizes need for more early strikes

KISSIMMEE, Fla. -- Marlins right-hander Carlos Zambrano battled through four innings on Wednesday and allowed three runs in an 81-pitch outing against the Astros. Zambrano, who allowed four walks in 4 1/3 innings of his start against the Cardinals last Friday, again was his own worst enemy against Houston, issuing five free passes.

"I have to work on throwing first-pitch strikes," said Zambrano, who has walked 14 batters and struck out 18 in 17 2/3 innings this spring. "Those walks are killing me in Spring Training. If I do walk people, I have to work on getting people out."

Facing the Astros for the first time this spring, Zambrano cruised through the first inning before a 32-pitch experience in the second frame in which he faced seven batters and surrendered just one run.

In the second, he issued back-to-back walks to Carlos Lee and Travis Buck to begin the inning. Marlins center fielder Emilio Bonifacio bailed Zambrano out on the next play when he fielded a single by Chris Johnson and threw out Lee at home.

Buck scored on a single to left by Chris Snyder, but Zambrano escaped any further damage by striking out Jose Altuve and, after allowing a single to Astros pitcher Lucas Harrell, forcing Brian Bogusevic into a groundout to second.

"Those plays certainly helped me, but I have to work on keeping guys off base," said Zambrano, who has a 5.09 ERA in five Grapefruit League starts.

Zambrano gave up two runs in the fourth inning while tossing 24 pitches. Once again, walks came into play as Zambrano allowed two of them early in the frame before surrendering a two-run single to Bogusevic later in the inning.

"He was a little off today, but I think he pitched well and his velocity is up," Marlins manager Ozzie Guillen said.

Zambrano, whose fastball has ranged from 92 to 93 mph this spring, will face the Yankees in a Monday night exhibition at Marlins Park, the first evening game against big league competition in Miami. It will be the last exhibition game for the Marlins before they open the season on April 4 at home against the Cardinals.

"It will be exciting to see the place and to be in front of our fans," Zambrano said.

Bench hopefuls on display as time running out

KISSIMMEE, Fla. -- Several players who are in the mix for a backup role with the Marlins were in the lineup on Wednesday.

Bryan Petersen started in right field, Chris Coghlan started in left, Donovan Solano started at shortstop and Donnie Murphy started at third base.

Aaron Rowand pinch-hit for Marlins starter Carlos Zambrano in the fifth inning, and took Emilio Bonifacio's place in center.

Manager Ozzie Guillen said he will get together with his coaches and Marlins management to discuss the backup positions.

Guillen said the status of left fielder Logan Morrison and right fielder Giancarlo Stanton will play a factor in the final decision. Morrison (right knee) and Stanton (left knee) have been taking part in Minor League games since the weekend, either as designated hitters or position players.

On Tuesday, both Morrison and Stanton each played five innings in the field for five innings.

On Wednesday, the two served as DH in Minor League action. If all goes well, they will be back in the outfield on Thursday.

Petersen went 2-for-4 on Wednesday, Coghlan went 1-for-4, Solano went 1-for-3 with a triple and a run, Murphy went 2-for-3 with an RBI and Rowand went 0-for-2. Petersen added his third stolen base of the spring and Murphy added his first.

"I like their aggressiveness," Guillen said. "Anything they can do to spark something is good."

Guillen once again praised Solano, who is batting .389 this spring.

"I like what he's been doing," Guillen said. "Nothing's set, but everything will be based on how [Morrison and Stanton] are."

Infante, Astros' Lowrie disagree on play

KISSIMMEE, Fla. -- Jed Lowrie voiced his displeasure about the pickoff play in the third inning in which the Astros shortstop sprained his right thumb.

On the play, Marlins starter Carlos Zambrano whipped the ball to Omar Infante, who had to stretch across the base to quickly place the tag down on Lowrie. In doing so, Infante stepped in front of the bag and blocked Lowrie's path back to the base.

Lowrie stayed on the ground for a few seconds, prompting Astros trainer Nate Lucero to run out to check on him. Lowrie got up and exited the game to have his thumb examined.

X-rays proved negative and Lowrie was diagnosed with a sprained thumb. He is day to day.

"Hopefully it's ice it a couple of days and I'm back out there," Lowrie said. "I'm going to go with that until they tell me otherwise. It's stupid with five days left in Spring Training. I don't think there's any reason to block a base at any time, particularly at this time. I don't think he's trying to hurt me, but he's a middle infielder. Stupid injuries like this happen when you block bases. Hopefully it's nothing."

Infante said he was simply making a play.

"I wasn't trying to hurt him or anything like that," Infante said. "I had to reach for the ball, and it just happened where I ended up in front of the bag."