HOUSTON -- Four months after undergoing surgery to remove the hook of the hamate bone in his left hand, Astros outfielder J.D. Martinez is anxious to get to Spring Training to see how the hand responds while swinging a bat regularly.

"I really haven't been able to swing that much yet, but I feel like it's right there and really close," he said. "I'm trying to rest it as much as I can now because I know when Spring Training starts, it's going to be non-stop. I feel like I'll be ready and it will be strong enough for me to do what I have to do."

Martinez, the Astros' Opening Day starter in left field a year ago, struggled for the first time in his pro career and was sent to the Minor Leagues. He hit .241 with 11 homers and 55 RBIs in 395 at-bats last season with the Astros after hitting .274 with six homers and 35 RBIs in 208 at-bats in his debut in 2011.

While he hasn't been able to swing the bat much this winter, he has been able to put in some defensive work with Cardinals outfielder Jon Jay at the University of Miami. Martinez's father went to school with Jay's father in South Florida.

"He's a really good outfielder and someone that knows the game for how young he is," Martinez said. "It's been great since the first day I met him. He's been helping me out tremendously."

Suspended Singleton to play in Minor League camp

HOUSTON -- Jonathan Singleton, the Astros' No. 1 prospect who will be suspended the first 50 games of this season after testing positive for marijuana, will participate in Minor League camp this spring. Houston general manager Jeff Luhnow believes he still could reach the majors in 2013 despite his setback.

Singleton, who was suspended Jan. 9, will be allowed to compete in spring games and could even get plugged into some Grapefruit League games.

"I think we've always thought this is the year Jonathan Singleton probably gets to the big leagues, whether it's the beginning, middle or end of the season," Luhnow said. "I think he's got a good shot. If he stays healthy and continues to produce, he'll be there."

Singleton will miss the first seven weeks of the season because of his second positive drug test, which means he'll lose about 200 at-bats that are crucial in his development. He hit .284 with 21 homers and 79 RBIs last year in 131 games at Double-A Corpus Christi.

"It's a setback because it's 50 games against high-caliber competition," Luhnow said. "He'll still be able to get swings, he'll still be able to participate in baseball activity down in extended [spring], but it's a little different facing pitchers and doing batting practice at extended than it is in [Triple-A] Oklahoma City and in Houston. It's a setback, no question about it, but hopefully it's also been a learning experience and something we can build on from here."

Castro looking forward to starting camp healthy

HOUSTON -- Astros starting catcher Jason Castro can only hope a terrific offseason will mean a breakout regular season is coming his way in 2013.

Castro, who married college sweetheart Maris Perlman in November and took a honeymoon to South Africa, said Friday he finally believes his knee problems are in the past. He expects to begin camp as healthy as ever and is eager to build on last year's strong finish.

"This is the best I've felt even before I had my first surgery," said Castro, who missed all of 2011 after tearing his right ACL during Spring Training that year. "I'm really happy with how that's gone, and I'm just looking forward to getting down to Florida."

The Astros eased Castro back into action last year with 257 at-bats. He got off to a slow start at the plate and responded to hit .281 with six home runs and 21 RBIs in his final 61 games, hitting four homers in the final seven games of the season.

"I made a few steps and I learned a lot from last year," he said. "Just from getting to play more than I had in a while and from a physical standpoint, I kind of know what I need to do with my body and how to take care of myself and everything.

"I'm really happy with where I'm at. I had kind of gotten used to not feeling good and that kind of became normal. I'm really excited about how I feel and what 100 percent actually feels like. I'm going to take that into spring and try to build on that."

Howe to be hitting coach for Team China

HOUSTON -- Former Astros, A's and Mets manager Art Howe will serve as hitting coach for China during this year's World Baseball Classic. Howe was asked by Chinese manager John McLaren to replace Wally Joyner, who took the job as assistant hitting coach of the Phillies.

"John called me and asked me if I'd be interested in being the hitting coach for the team, and I said, 'Yeah, why not?'" said Howe, who won 1,129 games in 14 years as a manager.

Howe, who lives in Houston and has served part-time as a pregame and postgame analyst on Astros television broadcasts the last few years, will leave at the end of the month for Arizona, where China will train at the Mariners' complex. The Chinese team will then fly from Phoenix to Japan for the first round of the Classic against Japan, Cuba and Brazil.

"I'm just going to go in and work with them individually during the spring and try to do what I can to make them better," he said. "The first part will be learning their names. That will be the real challenge to start with. I'm really looking forward to it. I've been to Japan a couple of different times and it's always nice to go there."