Jul 20, 2009 8:29 AM EST

The White Sox aren't willing to keep using Clayton Richard as their fifth starter if he continues to struggle.

Richard, who will pitch on Tuesday against the Rays, has won only once in his last eight starts.

Chicago manager Ozzie Guillen joked that President Obama's first pitch at last week's All-Star Game "was better than Richard's last outing."

Guillen also made comments that appeared to put Richard on notice. He must improve, or he'll lose his spot in the rotation.

"Yes, that's why we have him here now," Guillen said. "But this is not the Instructional League. I don't [want to] see another outing like the last few because we need to win.

"This ballclub is built to win and that's why he has to step it up a notch and do better."

Via Chicago Tribune