This month’s new headliner for The Ultimate Fighter 18 Finale is scheduled for three rounds rather than the usual five.

As MMAjunkie.com reported Sunday, UFC officials announced a knee injury has forced lightweight champion Anthony Pettis (17-2 MMA, 4-1 UFC) out of next month’s UFC on FOX 9 headliner with Josh Thomson (20-5 MMA, 3-1 UFC), and in its place, a bout between flyweight champion Demetrious Johnson (18-2-1 MMA, 6-1-1 UFC) and Joseph Benavidez (19-3 MMA, 6-1 UFC) has shifted from the TUF 18 Finale to UFC on FOX 9’s new headliner.

As a result, a third fight between lightweights Nate Diaz (16-9 MMA, 11-7 UFC) and Gray Maynard (11-2-1 MMA, 9-2-1 UFC) has been promoted from the TUF 18 Finale’s co-main event to its new main event. Due to the late notice, UFC officials subsequently confirmed the fight will remain a three-rounder instead of being a five-round non-title affair.

The TUF 18 Finale takes place Nov. 30 at Mandalay Bay Events Center in Las Vegas. The main card airs on FOX Sports 1 following prelims on MMAjunkie.com.

While the UFC recently instituted five-rounders for headlining non-title affairs, late-notice bouts are still usually scheduled for three rounds.

Now in the night’s main event, Diaz and Maynard meet for the third time, but just the second time officially. They fought the first time on “The Ultimate Fighter 5” with Diaz winning by submission. In January 2010, Maynard won their lone official fight by split decision.

Now their rematch and unofficial trilogy fight gets main-event status in Sin City.

The latest TUF 18 Finale card now includes:

Nate Diaz vs. Gray Maynard TBA vs. TBA – “TUF 18” men’s tournament final TBA vs. TBA – “TUF 18” women’s tournament final Walter Harris vs. Jared Rosholt Maximo Blanco vs. Akira Corassani Tom Niinimaki vs. Rani Yahya Sean Spencer vs. opponent TBA

For more on the TUF 18 Finale, stay tuned to the UFC Rumors section of the site.

(Pictured: Nate Diaz)