HOUSTON -- For a guy with a full no-trade clause on a team with no plans to trade him, Roy Oswalt is amused to find himself the subject of trade speculation.

"Hopefully they'll tell me before they trade me, I don't know when I'm getting traded," Oswalt joked Tuesday afternoon. "You heard anything?"

The Astros ace hasn't asked to be traded and hasn't been approached by the Astros, nor has he gotten word of any proposals. But with Houston 13 games out of first place in the National League Central and the halfway point of the season coming up this weekend, other teams have been watching Houston in the event the Astros decide to become sellers before next month's trade deadline.

In a thin pitching market Oswalt, signed through 2011 with a club option for 2012, would be a hot commodity that could bring a passel of prospects Houston's way were the Astros to decide to deal him. The Angels, Braves, Mets and Phillies are among the teams that have scouted Oswalt recently.

Oswalt, 6-7 with a 4.84 ERA, started slowly this season but has pitched well in two of his last three starts.

No team wants to deal an ace, but if the Astros do decide to rebuild, Oswalt's value on the trade market this year might be as high as it's going to get as the demand for pitching greatly exceeds the supply.

The Astros, however, aren't committed to selling.

"Veteran players always think that when you start to get closer to trade deadlines, they start to think, 'Well, maybe I might get moved,'" Astros manager Cecil Cooper said. "I'm sure it will probably go through a lot of guys' minds, but we're not thinking about that. We're thinking about winning."

"I don't think we're at that point at all," second baseman Mark Loretta said. "We're still not halfway through the season. We've shown glimpses of glory, enough to probably get everybody's hopes up and ours as well. I think it's too premature to think about [trades]."

Teammate Carlos Lee has a no-trade clause and isn't worried about getting traded.

"That's management's decision," Lee said. "There's nothing we can do about it. All we can do is go out there and play."

For his part, Oswalt says he hasn't thought about leaving the only professional organization he's known.

"I love Houston," Oswalt said. "Great fans, great city. They've been great to me."

Once upon a time, Billy Wagner felt the same way about the Astros. Wagner thought he might spend his entire career with Houston. But after eight years, Wagner, then 31, wanted to move on. Wagner was traded to Philadelphia during the winter of 2003.

What would Oswalt, who turns 31 in August and in his eighth year in Houston, do if the Astros are out of the race late next month and approach him with a trade proposal that would send him to a contending team?

"I don't know, they haven't approached me," Oswalt said. "If the owner comes up and asks me, we'll talk about it. The owner, GM, nobody has approached me about it."