WIMBLEDON, England -- Seven-time champion Pete Sampras may miss Wimbledon with an injury.

Sampras, who was scheduled to play on Centre Court on Monday morning, sustained what tournament officials described as an "acute strain in the lower right ribs" Saturday and pulled out of an exhibition match.

On Sunday, he asked Wimbledon organizers to schedule his first-round match -- against Britain's Martin Lee -- for Tuesday instead of Monday in order to give him more time to recover.

The All England Club rejected the request, saying it had already determined that Sampras' half of the draw would play Monday.

But, instead of scheduling Sampras for the first match on Centre Court as expected, the club put him on for the third match. That would give him a few extra hours of rest and treatment.

Sampras' coach, Jose Higueras, said Sampras didn't practice Sunday and was receiving ultrasound treatment. He said his status was day-to-day.

"We'll have to see how he feels when he wakes up tomorrow,'' Higuera said. "I think he'll play. Hopefully he will be fit. We'll see.''

Sampras was due to play Stefan Koubek at the Boodle & Dunthorne Championship on Saturday as part of a final tuneup for Wimbledon.

But Sampras said he felt a "slight tweak'' during practice and decided not to risk further injury before Wimbledon.

"As a result of sustaining an acute strain in the lower right ribs on Saturday, Pete Sampras requested a Tuesday start,'' Wimbledon referee Alan Mills said in a statement. "Since we had already determined his half of the draw would play on Monday, we were unable to grant this particular request.

"However, as is the case with all players who ask for a late start, we were able to help him by putting him on third match on Monday.''

By tradition, the defending men's champion opens Centre Court play. But last year's winner, Goran Ivanisevic, is out following shoulder surgery. And the losing finalist, Pat Rafter, is taking an extended break from tennis.

Sampras, who won his record seventh Wimbledon singles title in 2000, had been widely expected to get the Centre Court honor -- even though he is seeded only No. 6 this year.

Instead, No. 3 Andre Agassi -- the 1992 champion -- will open on Centre Court against Israel's Harel Levy.