Jake Shields (Pictures) will not fight Drew Fickett (Pictures) in San Jose, Calif., this Saturday.

The ranked welterweight withdrew from his EliteXC 170-pound title fight Tuesday morning after his father and manager, Jack Shields, determined that a weakened lower back could hamper the highly-regarded San Franciscan during the bout.

"I kept going back and forth thinking I could tough it out and get through it hurt," said Shields, who told Sherdog.com the injury occurred last week as he performed cardio drills with a heavy hammer. "I felt maybe when I'm warm and suck it up, it wouldn't hurt during the fight. I thought I could ignore it. But my dad was worried I'd throw it out bad doing that."

Bed ridden for several days, Shields, 29, said the injury improved to the point where he could walk on his own, but "can't quite workout."

Shields, a newly promoted Brazilian jiu-jitsu black belt under Cesar Gracie (Pictures), was scheduled to fight Fickett in a featured bout on the Showtime-televised co-promotion between EliteXC and Strikeforce.

"I was in great, great shape," said Shields (20-4-1). "I was feeling unstoppable until I threw my back out. But I guess it's better to dominate Fickett than go out there and lose because I'm hurt."

EliteXC promoter Gary Shaw told Sherdog.com that Fickett (32-5) would likely be moved to the undercard. According to Fickett's manager, Bryan Hamper of XR Fighting Management, event promoters are in the process of looking for a licensed opponent to fight the 28-year-old Arizona-based UFC veteran.

Presuming he wins, Fickett will meet Shields June 14 in Honolulu, Hawaii, EliteXC Vice President Jared Shaw told Sherdog.com. The Showtime-televised card will also feature a 160-pound title fight between champion Karl James Noons (Pictures) and Yves Edwards (Pictures), which was rumored to appear May 31 on CBS. Kala Kolohe Hose (Pictures) is also slated to appear on the card.

Tommy Messano contributed to this report