The UFC 173 opening main card bout ended in a rare injury TKO, and it probably should've ended much earlier. Lightweight Jamie Varner hurt his left ankle about a minute into the first round of his bout against James Krause, and had problems standing upright for the duration of the round. He even shot a double-leg takedown just to prevent the fight from staying on the feet, but Krause eventually got out of harm's way and they returned to striking.
Varner had his lower leg peppered by Krause's kicks, and any sort of movement and shiftiness from Varner was met with him awkwardly limping or falling to the canvas. On three different occasions he was unable to stand, but referee Jason Herzog let the fight continue to the end of the 1st round. Varner confirmed to his corner that he had indeed broken his ankle, which forced the doctor to immediately stop the fight.
Why Herzog allowed the fight to go on despite the obvious signs that Varner couldn't maintain his balance is a bit puzzling to me. Varner has been lauded for his toughness for spending virtually the entire round hobbled and wobbled, but unfortunately it's a 3rd straight loss for him as he falls to 21-10-2 (2 NC). Krause moves to 2-1 in the UFC and 21-5 in his career.