“The Ultimate Fighter 18” winner Julianna Pena (5-2 MMA, 1-0 UFC) sustained “a very severe knee injury,” according to a rep from her training camp, and will be unable to fight Brazilian Jessica Andrade (10-3 MMA, 1-1 UFC) at UFC 171.

The rep, who asked for anonymity because he wasn’t authorized to discuss the matter, told MMAjunkie the injury occurred “a couple of days ago” and said Pena is headed to Los Angeles for surgery with a UFC-recommended specialist.

The rep shot down a rumor that Pena was pregnant and was forced to forgo the fight, which was set for the March 15 pay-per-view event at Dallas’ American Airlines Center.

A UFC official told MMAjunkie that the search for a replacement opponent is underway. One volunteer already has made herself known: Sarah Kaufman. The former Strikeforce champ today tweeted “Please … With Pena out I want in at #ufc171! Back to Texas and this time judges won’t be able to get it wrong.”

Kaufman is referring to her most recent fight, which ended in a split decision loss to fellow UFC newcomer Jessica Eye. The 28-year-old Canadian holds wins over UFC vets Alexis Davis, Liz Carmouche, Roxanne Modaferri and Miesha Tate.

Pena was an early favorite on “TUF 18” and stopped two of three opponents in the reality-show tournament before earning a first-round TKO of finalist Jessica Rakoczy to win the “TUF” crown. Prior to her UFC debut, she had lost two straight on the regional circuit.

Andrade made her debut at this past July’s UFC on FOX 8 and lost to onetime title challenger Carmouche via second-round TKO. She rebounded at this past October’s UFC Fight Night 30 with a dominant decision over vet Rosi Sexton.

For the latest on UFC 171, stay tuned to the UFC Rumors section of the site.

(Pictured: Julianna Pena)