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3/20/2014 5:34 P.M. ET

Gonzalez could allow Astros to carry extra pitcher

KISSIMMEE, Fla. -- Astros manager Bo Porter said the decision whether to carry 12 or 13 pitchers, which means seven or eight relievers, to open the season will depend on the composition of the roster when it comes to position players.

The one player who could swing the decision is Marwin Gonzalez, who entered Thursday second among Grapefruit League hitters with a .441 batting average through 17 games. Gonzalez's versatility -- he can play third base, shortstop, second base and the outfield -- could mean the Astros could carry an extra arm if he makes the club.

"That's a big factor," Porter said when asked about Gonzalez. "The fact not only the spring he's having from an offensive standpoint, the flexibility he gives us being able to play a multitude of positions. We've put him in the outfield, he's going to see time at first base. We're going to get him in center field one of these games here.

"Having a guy that can play that many positions ... we always knew defensively what we have, but offensively, he's worked extremely hard on his game. There's not many fly balls anymore; it's hard ground balls and line drives, and I think he's really understanding who he is as an offensive player and has helped them tremendously."

With latest start, Harrell back on right track

KISSIMMEE, Fla. -- Coming off a rough outing in his previous start on Saturday against the Tigers, right-hander Lucas Harrell righted the ship Thursday afternoon and stated his case to make the Astros' rotation by holding the Phillies to six hits and one run in 4 1/3 innings.

Harrell, who's among four battling for the final two spots in the rotation, has allowed one earned run in four of his five starts this spring. The aberration was a 12-hit, nine-earned run effort against the Tigers that did a number on his spring ERA.

"Some of the good things I've been taking out of my outings are weak contact," Harrell said. "I felt like I got some weak contact today, some balls on the ground, and that's mainly what I'm looking for. "

Astros manager Bo Porter was pleased with the way Harrell attacked the zone and used his curveball early in counts and a couple of times to get himself back into counts Thursday. Harrell, who's out of options, will have at least one more outing.

"Every time is crucial, I feel like," Harrell said. "As a person that's a competitor, I want to go out and pitch every time. I don't care. My next time out I definitely need to throw well to give myself a chance to make this team."

Astros, Dominguez nearing contract extension

KISSIMMEE, Fla. -- The Astros are closing in on a five-year contract extension with third baseman Matt Dominguez worth around $17 million with a pair of club options, according to a Yahoo report.

The tweets on Thursday about the contract talks said the extension could take time to finalize, and also said the Astros have talked with outfielder Robbie Grossman and catcher Jason Castro about extensions.

The Astros did not comment.

Dominguez, 24, played in 152 games last season and hit .241 with 21 homers and 77 RBIs while playing top-notch defense at third base. Dominguez will be eligible for arbitration for the first time in 2016, while Grossman wouldn't be arbitration-eligible until 2017.

"Houston's my home and I love being an Astro," said Grossman, who grew up in the Houston area. "I want to be here as long as possible."

Like Grossman, Dominguez didn't want to comment on any potential contract talks.

"I like the city of Houston and I like playing here," he said. "If it happens, it happens. If they were to come to me and do that, I don't know. I'm just taking it day by day."

Astros general manager Jeff Luhnow has said repeatedly he'd like to sign Castro to a contract extension at some point. Last year, the Astros signed Jose Altuve to a budget-friendly four-year deal, and FOX Sports reported Wednesday they had offered prospect George Springer a seven-year, $23-million deal, which he turned down.

Cosart, Oberholtzer to follow Feldman in rotation

KISSIMMEE, Fla. -- Astros manager Bo Porter announced two more spots in the pitching rotation Thursday, saying right-hander Jarred Cosart would start the second game of the regular season -- on April 2 against the Yankees -- and left-hander Brett Oberholtzer would take the third game of the season the following day. Scott Feldman was previously announced as the Opening Day starter.

Cosart got the news one day after he retired all 15 batters he faced in a dominating performance against the Nationals, striking out nine batters. Cosart was 1-1 with a 1.95 ERA in 10 starts last year in his Major League debut.

"For me, you look at what Jarred Cosart was able to do last year, I was pretty comfortable with him being one of the guys who was going to be in our rotation," Porter said. "Last night, you got a chance to see a guy who has an opportunity to be a front-of-the-rotation guy. When he's locked and if we get that type of consistency, he's going to pitch to his potential."

Cosart, who grew up in Houston, said he's a huge fan of Derek Jeter, the Yankees shortstop who will be making his final appearance in Houston during the series against the Astros. Cosart said to be in the rotation to start the year is an honor.

"My future goal is to be a No. 1 one day," he said. "There's no one more deserving this year than Scott. He's helped us young guys out a lot. Now we're kind of going with the mindset we're trying to [start off on] the right foot, and that would be to win a series. That's our goal."

Oberholtzer was impressive as a starter as a rookie in 2013, going 4-5 with a 2.24 ERA in 10 starts.

"It's a great opportunity, for one," he said. "But it's also an honor to be named as one of the five to break as Opening Day starters. It's something I had in mind to make an Opening Day roster since I was young. It's a dream come true, and hopefully I can continue the success I had last year for many years to come."

Porter said right-handers Lucas Harrell, Jerome Williams and Brad Peacock and left-hander Dallas Keuchel are the remaining candidates for the final two spots in the rotation.

"As we work through the competition for those final spots, all the guys taking the ball this next turn through, they all realize what's at stake," Porter said.

X-rays show no fracture on Correa's hand

KISSIMMEE, Fla. -- The Astros breathed a huge sigh of relief Thursday when X-rays performed on the left hand of shortstop prospect Carlos Correa showed no fracture. Correa left Wednesday's game after he was hit on the hand.

"No fracture at all, so it's good," said Correa, the top pick in the 2012 First-Year Player Draft. "It's a little bit sore, but it'll be fine by tomorrow."

Correa, 19, was reassigned to Minor League camp on Thursday, but he impressed the Astros by how he handled himself on and off the field. Manager Bo Porter was extremely concerned when Correa went down after Tyler Clippard of the Nats struck him with a fastball Wednesday.

"It's a scare, but part of what helps is he turned the right way," Porter said. "He gave way a little bit and that lessened the blow a little bit. Needless to say, we're definitely excited about the news we received. It's just a little bit sore."

Worth noting

• Right-hander Mark Appel, the No. 1 pick in last year's First-Year Player Draft, will pitch in a game for the first time Friday when he takes the mound in a Minor League contest. He's been slowed this spring after undergoing an appendectomy in January.

• Right-hander Brad Peacock, who's one of four pitchers competing for the final two spots in the starting rotation, will pitch in a Minor League game on Friday.

Brian McTaggart is a reporter for MLB.com and writes an MLBlog, Tag's Lines. Follow @brianmctaggart on Twitter. This story was not subject to the approval of Major League Baseball or its clubs.