The highly anticipated UFC Fight Night main event clash between Calvin Kattar and Arnold Allen ended with an unfortunate injury.Kattar hurt his right knee after missing a leaping attack late in round one. In the second, Allen landed a leg kick and Kattar dropped as he was unable to plant his back leg. With 'The Boston Finisher' obviously injured, referee Herb Dean called for the TKO stoppage within the first eight seconds of round two.UFC@ufcNot the way anybody expected this one to goThis one will go down as a TKO for @ArnoldBFA after Kattar suffers a knee injury #UFCVegas631144111Not the way anybody expected this one to goThis one will go down as a TKO for @ArnoldBFA after Kattar suffers a knee injury #UFCVegas63 https://t.co/bPthoJOzwdAllen snagged his 10th straight victory in the UFC, but admitted that he was unhappy with how it came about.UFC@ufcBack in the win column! @MaxPainGriffin takes the split decision over Tim Means in our #UFCVegas63 co-main 24920Back in the win column! @MaxPainGriffin takes the split decision over Tim Means in our #UFCVegas63 co-main 👏 https://t.co/kJX4DsMDbrIn the co-main event, Max 'Pain' Griffin earned a close split decision win over Tim Means. After three rounds, a pair of judges agreed that Griffin had done enough to win the fight, awarding him with scores of 29-28 and 30-27.UFC@ufcWelcome to the UFC Waldo Cortes Acosta! The UD victory at #UFCVegas63 improves him to a perfect 8-0 20325Welcome to the UFC Waldo Cortes Acosta! The UD victory at #UFCVegas63 improves him to a perfect 8-0 👊 https://t.co/gYmwZqjvsfWaldo Cortes-Acosta kept his unbeaten record intact against Jared Vanderaa. Cortes-Acosta, a Dana White’s Contender Series (DWCS) winner, survived his opponent's leg kick-heavy offense and landed heavy swings to secure the win.UFC@ufcTresean Gore’s first UFC victory is a HUGE one #UFCVegas632123287Tresean Gore’s first UFC victory is a HUGE one 🔥 #UFCVegas63 https://t.co/LQiB2kdaRxIn the middleweight division, former The Ultimate Fighter (TUF) contestant Tresean Gore finally earned his first UFC win. In round two, 'Mr. Vicious' caught Josh Fremd in a guillotine choke. Refusing to tap out, Fremd paid with his consciousness, giving Gore the victory.UFC@ufc🗣 BY SPLIT DECISION!@KhalilRountree takes the W in a razor close fight - how did you score that one? #UFCVegas63134676🗣 BY SPLIT DECISION!@KhalilRountree takes the W in a razor close fight - how did you score that one? #UFCVegas63 https://t.co/ojRnSKTzH5Finally, a light heavyweight showdown between Khalil Rountree and Dustin Jacoby kickstarted the main card. After three rounds, Rountree snagged a controversial split decision victory.UFC Fight Night: Calvin Kattar vs. Arnold Allen resultsMain CardArnold Allen def. Calvin Kattar via TKO (knee injury) – Round 2, 0:08Max Griffin def. Tim Means via split decision (29-28, 28-29, 30-27)Waldo Cortes-Acosta def. Jared Vanderaa via unanimous decision (30-27, 29-28, 29-28)Tresean Gore def. Josh Fremd via submission (guillotine choke) – Round 2, 0:49Khalil Rountree def. Dustin Jacoby via split decision (29-28, 28-29, 29-28)Preliminary CardRoman Dolidze def. Phil Hawes via knockout (punches) – Round 1, 4:09Marcos Rogerio de Lima def. Andrei Arlovski via submission (rear-naked choke) – Round 1, 1:50Junyong Park def. Joseph Holmes via submission (rear-naked choke) – Round 2, 3:04Steve Garcia def. Chase Hooper via TKO (punches) – Round 1, 1:32Cody Durden def. Carlos Mota via unanimous decision (30-27, 29-28, 29-28)Christian Rodriguez def. Joshua Weems via submission (anaconda choke) – Round 1, 4:07