KISSIMMEE, Fla. -- When pressed on Thursday about who he plans to use in the closer's role year, Astros manager Brad Mills remained non-committal. Mark Melancon spent most of the 2011 season at closer, but was shipped to the Red Sox in December.

"We're having discussions as we speak," Mills said. "We've talked about some things and talked about some guys as we go forward, and we're constantly doing that. We're talking about names and different guys we might give the opportunity and see how things go. It comes down to what we see in Spring Training and in some of these games, and also who we feel would do the best job."

The Astros, who converted only 25 of 50 save chances last year, have several candidates. Veteran closer Brandon Lyon could step back into the role, but he missed most of last year following major arm surgery. Youngster David Carpenter could also be an option.

For now, Mills isn't naming names.

"I don't think that would be fair to a lot of guys if I did that," he said. "I don't think we need to get into that right now. You can sit down and look at the roster and look at a lot of the names and go from there. There might be a couple of surprises here and there. We're going to hold off on that right now, and it will start clearing up in the next few weeks."

Wandy not concerned about back tightness

KISSIMMEE, Fla. -- Left-hander Wandy Rodriguez had to cut short his bullpen session Wednesday, when he felt some tightness in his lower back. He told the team's athletic trainers and manager Brad Mills it wasn't anything to be concerned about.

"I just felt it a little bit, but I'm OK," Rodriguez said. "I just stopped because I felt something like it was tight. It was my second bullpen, so I need to take time until I feel better."

Mills didn't appear to be too worried.

"He threw the ball well, but his back was tight," he said. "It's not anything to be concerned about. That's out of Wandy's mouth, and the trainer said the same thing."

Rodriguez was the Astros' best starting pitcher last year and is a candidate to start on Opening Day. He was 11-11 with a 3.49 ERA in 30 starts in 2011 and has won at least nine games in each of his seven Major League seasons.

Former Mets top prospect Martinez reports

KISSIMMEE, Fla. -- Among the position players who reported to camp early Thursday were infielders Scott Moore, Joe Thurston and Diory Hernandez and outfielders Jason Bourgeois and Fernando Martinez, a former top prospect with the Mets.

Widely considered one of baseball's top prospects from 2006-10, Martinez was billed as a power-hitting outfielder expected to be a cornerstone of the Mets' lineup throughout this decade. But multiple injuries and an arthritic right knee have prevented Martinez from appearing in more than 82 games in any of the past three seasons.

"I'm really happy to be here, to be on a team and have new competition," Martinez said. "My whole career I played for the Mets, and right now I have a new home and I feel very grateful to be here."

Martinez, 23, spent the majority of the 2011 season at Triple-A Buffalo, but did have a brief stint with the Mets. In 63 games with Buffalo, he hit .260 with eight home runs and 30 RBIs.

Astros manager Brad Mills isn't ready to say if Martinez will get more time in left field or right field. He's played all three outfield positions for the Mets in his brief Major League career.

"We'll go through drills and see how he throws the ball and see his movements at the corner positions, and we'll go from there," he said. "To sit here and label him, I don't know enough about him or have seen him or talked to him [enough] to give you an educated answer."

Martinez has one option remaining, so if he doesn't make the Major League roster he could begin the season at Triple-A Oklahoma.

"I have to work hard, and if I play very good here, they could give me the opportunity to play in the Majors this year," Martinez said.

First-rounders Springer, DeShields form bond

KISSIMMEE, Fla. -- George Springer and Delino DeShields Jr., the Astros' two most recent first-round picks, have formed a bond during the early days of their first Major League camp. They are roommates this spring and have adjoining lockers in the clubhouse.

"We spent a lot of time together in the instructional league, and we hung out a lot, too," said DeShields. "He's a pretty cool dude, and we get along good."

DeShields, 19, was taken with the No. 8 overall pick of the 2010 First-Year Player Draft out of College Park, Ga., and last year made the transition to second base from outfield. He's ranked as the team's eighth-best prospect entering the season by MLB.com.

Springer, 22, was the 11th pick in the 2011 Draft out of the University of Connecticut and is facing his first full season in professional baseball. He played just eight games for short-season Tri-City after signing last year and is ranked as the team's No. 3 prospect by MLB.com.

"It's an unbelievable experience," Springer said. "I'm extremely fortunate to be here and see guys who've been here for three-plus [years] and how they handle everything and go about their business."

Worth noting

• Left-handed relief pitcher Sergio Escalona is nursing some elbow discomfort, but is expected to take his turn in the bullpen on Friday.

• The pitchers will throw while hitters are standing in the box during the first full-squad workout on Sunday, but the players won't take their first hacks against live pitching until Monday.