Welterweight contender Josh Koscheck has a bulging disk in his back and will not compete at UFC 151 on Sept. 1.

UFC revealed Koscheck's injury Tuesday night during its "Insider" program on Fuel TV.

Koscheck was scheduled to face Jake Ellenberger in the UFC 151 co-main event.

UFC announced Wednesday that Ellenberger will now face veteran Jay Hieron on the card.

Ellenberger (27-6) looks to rebound from a second-round knockout loss on June 1 to Martin Kampmann. The setback snapped Ellenberger's six-fight win streak.

Hieron returns to UFC for the first time since October 2005. And he is no stranger to Ellenberger.

"It's awesome. I feel great. It's been a long time coming," Hieron told ESPN.com. "It's the perfect time for me to get back in.

"We actually fought back in June 2006 and I won (by unanimous decision). I beat him before and I believe I can beat him again.

"I've cornered guys who've fought him. My teammate Mike Pyle fought him, but Jake beat him. And recently Martin Kampmann fought him and I cornered (Kampmann) and Martin beat him."

Hieron improved to 23-5 on July 13 with a second-round submission of Romario da Silva at Legacy Fighting Championship 12 in Houston.

Light heavyweight champion Jon Jones is slated to defend his title against hard-hitting Dan Henderson in the UFC 151 main event at Mandalay Bay Events Center in Las Vegas.

It will be Jones' fourth title defense.