Welterweight contender Josh Koscheck has reportedly been forced to withdraw from his featured 170-lbs. bout against Paulo Thiago at UFC 109 due to an undisclosed injury suffered in training.

The nature of Koscheck's injury is not yet known and the UFC is expected to find a replacement opponent for Thiago.

Koscheck has since confirmed his injury and exit from the UFC 109 card on his official Twitter account.

"Well the news is out," Koscheck's post read. "I am not fighting feb 6 UFC 109. Do due to injury. I will be good to go back to training in a couple weeks I hope!!"

This is the second time the UFC 109 main card has been hit by the injury bug, as an ankle injury first forced Antonio Rogerio Nogueira to withdraw from his co-headlining light-heavyweight bout against Brandon Vera.

Koscheck was looking to avenge a loss to Thiago from their first meeting at UFC 95 last February, where Thiago scored a shocking upset win over Koscheck via first-round TKO.

Koscheck (14-4) has won his last two bouts, defeating Frank Trigg at UFC 103 in September and, most recently, scoring an impressive second-round submission win over Anthony Johnson at UFC 106 last month. The win over Johnson earned him two Fight Night bonuses, which totaled a staggering $140,000.

Thiago (12-1) improved his UFC record to 2-1 in his latest bout by defeating UFC newcomer Jacob Volkmann via unanimous decision at UFC 106 on Nov. 21. 

UFC 109 takes place on Feb. 6 at the Mandalay Bay Events Center in Las Vegas, NV, and is headlined by a light-heavyweight battle between UFC Hall-of-Famers Randy Couture and Mark Coleman.

Make sure to check back with us the day of the event for free, live, round-by-round coverage of UFC 109 right here at FiveKnuckles.com! Join expert analyst Mike Williams as he takes you through the entire fight card blow-by-blow and then keep it right here for all the post-fight news and notes you can handle!