North Texas native Errol Spence Jr. beat out Kell Brook for the IBF Welterweight Title on Saturday in England.
Backed by most of the 27,000 spectators at Bramall Lane in his Sheffield hometown, Brook met Spence on even terms in the first eight rounds.
But Brook's left eye began to swell, and he was knocked down in the 10th round. With his left eye almost closed, he took a knee in the 11th and referee Howard Foster agreed to end the contest.
Spence, who owns a 22-0 record with 19 knockouts, relieved Brook of the welterweight title in his fourth defense.
Brook, at 36-2, lost for a second straight time after an ill-fated attempt to move up two divisions to middleweight and take on Gennady Golovkin eight months ago.
After the championship, Spence sent out this tweet.