While a showdown between UFC light heavyweight champion Rashad Evans and former champion Quinton “Rampage” Jackson appears inevitable, there are no guarantees it will happen at UFC 98 on May 23.

The Evans vs. Jackson matchup gained a great deal of intrigue following their impromptu war of words in the center of the Octagon following Jackson’s decision victory over Keith Jardine at UFC 96 this past Saturday. However, a date and a venue for their fight is uncertain.

What appears to be a certainty is that Evans’ first title defense will in fact be substituted for the UFC 98’s originally planned main event of UFC heavyweight champion Brock Lesnar vs. interim UFC heavyweight champion Frank Mir.

Mir confirmed during this weekend’s telecast that he underwent knee surgery last week and that he expects his rematch vs. Lesnar to happen now later in the summer. Evans’ first defense had been scheduled for UFC 100 on July 11 but UFC President Dana White confirmed in a video blog that Evans’ first fight since his title win over Forrest Griffin at UFC 92 has been moved up.

During the video blog, White was depicted as informing Jackson backstage that he had been awarded a $60,000 bonus for fight of the night. He went on to inform Jackson that Mir was out and that Evans’ first defense was chosen as a replacement.

“… We want to know if you want to fight Rashad on May 23? Frank Mir had knee surgery (and) he’s out of the fight so we’ve moved Rashad,” said White.

White later added that Jackson was being offered the slot but that Lyoto Machida would get the title shot if Jackson declined to take the fight.

“Let’s say you can’t or don’t want to take the fight then Machida would take the fight,” he said. “But we won’t make the decision until you go to the doctor and get your [expletive] checked out and make sure you okay.”

White’s latter statement was a reference to Jackson’s earlier revelation that he has been suffering from a lingering jaw injury.

“Yeah, I’m feeling alright,” Jackson responded when asked by White how he felt, before adding, “I just got to get my jaw [inaudible]. I didn’t never tell you, I hurt my jaw right before the Wanderlei fight. I didn’t never tell you I messed it up. I think I’ll be alright.”

When asked how he hurt it, he mentioned that the injury after being hit by an uppercut delivered by former UFC light heavyweight Hector Ramirez during a sparring session a work before Jackson’s victory over Silva at UFC 92.

In addition to the injury concern, Jackson added further doubt as to whether he’d accept the May 23 fight date. He indicated to White that he believed he over-trained for the Jardine fight and that he was looking forward to a break. If he accepted the UFC 98 fight vs. Evans, he would have to begin his training camp for the fight within two weeks, most likely in Big Bear, Calif.

While Jackson told White that he’s “got his back,” he closed out the conversation by saying that he needed a few days before giving him his final decision so that he could speak with his manager.