In an odd fight, the former WEC lightweight champion toughed out his injury, but had his leg give out on him three times over the course of the round.
And while referee Jason Herzog didn't seem to think anything of it, the ringside doctor immediately waved off the bout at the end of the first round, giiving Krause the win via injury TKO at the MGM Grand Garden Arena.
"I'm so sorry you missed out on an even better fight," Krause said in his postfight-interview. "He's such a tough guy and such a great competitor."
Varner (22-9-1, 2 NC), who was helped out of the Octagon by his seconds to an ovation from the crowd, has now dropped four of five bouts since he returned to the UFC.
As for Krause (21-5), the Missourian improved to 2-1 in the UFC and won for the ninth time in his past 10 fights.
"We worked on the kicking the calf extremely low," Krause said. "You know, Jamie is such a good competitor and it is such an honor to fight him."