CHICAGO -- What was turning into a classic bout ended in a way no one really wanted.

Tony Ferguson defeated Donald Cerrone by TKO at the end of the second round Saturday at UFC 238 when it was ruled by ringside doctors that Cerrone could not continue. Cerrone's right eye was swollen shut after a dominant second round by Ferguson.

It was a back-and-forth, bloody encounter until that point between two of the best lightweights and most popular fighters in the world.

At the end of the second round at United Center, Ferguson landed a right hand on Cerrone's face after the bell. Referee Dan Miragliotta ruled after watching a replay that, though the punch landed, it didn't hit Cerrone in the eye, but the nose. Miragliotta said it therefore was not a foul that directly caused the finish and Ferguson would win by TKO.

Had Miragliotta ruled the foul caused the finish, it would have been a disqualification or no contest.

"The punch had nothing to do with it," Cerrone said afterward. "That was the fight I think everybody wanted. I don't quit, I don't back down. I just want to keep fighting."

Cerrone won the first round, bloodying Ferguson with hard jabs and right hands. In the second, Ferguson took over as the body kicks he landed in the first round began to add up. Ferguson landed a barrage of jabs and straight rights to bust up Cerrone's nose and leave him bloody. Ferguson also smashed Cerrone with a spinning back elbow.

The end of the round and the way it finished marred what was becoming one of the year's best fights.

"It's not how I wanted the fight to go," Ferguson said. "It's really emotional in here."

UFC president Dana White said at the postfight news conference that Cerrone was transported to the hospital because of a broken right orbital bone.

Ferguson (26-3) is the pretty clear-cut No. 1 contender to the lightweight title after the victory. But the 35-year-old nicknamed "El Cucuy" said he would be OK with a Cerrone rematch next.

"We can throw it back, I don't mind doing that," Ferguson said. "I really don't. He's a hell of a f---ing fighter."

Cerrone (36-12, 1 NC) had his three-fight winning streak snapped with the defeat.