Oswalt, whose contract expires at the end of the 2011 season, has a full no-trade clause and would have to approve any trade from the Astros. General manager Ed Wade doesn't discuss trades, but acknowledged last month Oswalt's agent had asked for a trade.
The Astros aren't believed to be actively shopping Oswalt, and a trade would be challenging considering Oswalt's desire to play for a contender, the large amount of money remaining on his contract and the caliber of prospects the Astros would likely want in return.
Oswalt is 3-7 with a 2.78 ERA in 11 starts this year. He began the season with 10 consecutive quality starts before being ejected in the third inning of Monday's game against the Nationals for what was deemed showing up an umpire.