The Associated Press

SAN DIEGO - Sammy Sosa felt a bit sheepish while explaining why he wasn't able to play Sunday against the San Diego Padres.

He sneezed twice shortly after arriving in the clubhouse before the game, which brought on back spasms and forced him to grab a chair to support himself. Sosa spent the afternoon in the trainer's room receiving treatment.

The Cubs are off today before opening a homestand on Tuesday.

"I don't feel too good," Sosa said. "If I'm ready, I'm going to play. If I'm not ready, I'm not going to play. Whenever I feel 100 percent, I'll be back."

INVESTIGATION: Baseball is checking whether a Diamondbacks pitching prospect used his nephew's identity to sign with the team, making him appear three years younger, according to documents obtained by The Associated Press.

Birth records show that Adriano Rosario's real name is Ramon Antonio Pena Paulino, and that he was born Jan. 9, 1982, making him 22. The real Rosario, who is Pena's nephew, turned 19 Sunday, according to the documents.

Sandy Alderson, executive vice president of baseball operations in the commissioner's office, said that there is an ongoing investigation.

SHORT HOPS: The Colorado Rockies recalled right-hander Allan Simpson and sent infielder Aaron Miles to Triple-A Colorado Springs on Sunday in an attempt to bolster their battered pitching staff.

• The Kansas City Royals placed outfielder Aaron Guiel on the 15-day disabled list Sunday because of blurred vision in his left eye and called up infielder Wilton Guerrero from Triple-A Omaha.