HOUSTON -- Pirates starter Shawn Chacon flew back to Pittsburgh today to have a sore right knee examined. The injury is not thought to be serious, but its exact nature is not yet known.

Chacon, acquired two weeks ago from the New York Yankees, lasted only 1 2/3 innings last night against the Houston Astros and was charged with seven runs in what wound up a 14-1 blowout. Manager Jim Tracy said Chacon's first complaint about the knee came after the game and that the soreness is on the outside of the knee.

Also, reliever Josh Sharpless will be unavailable to pitch in the series finale tonight because of a sprained right ankle. Tracy said it is possible Sharpless will miss more time but added he could be back by the weekend.

He was injured last night while fielding a ground ball.

More details in tomorrow's Pittsburgh Post-Gazette.