Former lightweight champion Sean Sherk's surprise return to California -- where he says he was falsely accused by the state athletic commission of taking steroids in 2007 -- just wasn't meant to be.

"The Muscle Shark" has been forced out of an upcoming 155-pound tilt opposite Gleison Tibau at UFC 104: "Machida vs. Shogun," opening up the door for the always-game Josh Neer to take his place inside the Octagon at the Staples Center in Los Angeles, Calif., on Oct. 24.

Sherdog.com reports that Sherk sustained a shoulder injury in training that will keep him out of action four at least four weeks, which would seriously cut in to his preparation for the Brazilian.

It's a good thing "The Dentist" makes house calls.

Neer is coming off a frustrating unanimous decision loss to Kurt Pellegrino at UFC 101 on Aug. 8, during which he was stifled by the wrestling and ground skills of "Batman" for most of the 15-minute scrap. It was no doubt a tough pill to swallow for the Des Moines, Iowa, native because he has yet to string together consecutive wins since returning to the promotion in early 2008.

Neer was looking to build off a "Fight of the Night" winning performance over Mac Danzig at UFC Fight Night 17 earlier this year, which prompted the UFC to award him with a contract extension. It was his second bonus in as many fights -- he dropped a different "Fight of the Night" in a three-round war against Nate Diaz before the win over Danzig.

His ability to electrify the crowd with his aggressiveness is among the best in the division; however, he may have a difficult time sparking fireworks against another talented Brazilian jiu-jitsu specialist.

Tibau is also coming off a decision loss (split) after Melvin Guillard took him the distance at the TUF 9 Finale less than a month ago. It snapped a two-fight win streak for the Brazilian, who’s been up and down since his debut against Nick Diaz at UFC 65 way back in November 2006.

The streaking American Top Team (ATT) product followed the Diaz loss by winning his next three fights inside the Octagon before dropping consecutive bouts to perennial division threats Tyson Griffin and Joe Stevenson.

UFC 104 features the first title defense for undefeated light heavyweight champion Lyoto Machida against fellow Brazilian Mauricio "Shogun" Rua in the main event of the evening. In addition, rising talent Cain Velasquez and veteran Ben Rothwell will "wage war" in a super-sized heavyweight showdown.

To check out the latest UFC 104: "Machida vs. Shogun" fight card and rumors click here.