SHEFFIELD, England - Kell Brook lost his IBF welterweight belt when mandatory challenger Errol Spence Jr. stopped him in the 11th round on Saturday.

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 waved off the contest as Brook took the full count.

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 suffering a fractured left orbital bone in the fight, Brook is looking at potential surgery.

When he returns to the ring, Brook is looking to campaign as a junior middleweight.

There are still opportunities at welterweight, with Brook's rival Amir Khan calling for a fight and the possibility of a rematch with Shawn Porter.

But former world champion and Sky Sports analyst Johnny Nelson is advising Brook to completely forget about the welterweight division and focus all of his energy on campaigning in the future as a junior middleweight.

"Kell will carry on, but to me it can't be at welterweight," Nelson told Sky Sports. "What he will do is go back, lick those wounds and then come back at light-middle. He'd be mad to come back at welterweight. Light-middleweight - or super-welterweight - that is where his strength lies.

"He wasn't as strong in the second half as he'd been in the first half and was manhandled and pushed back by Errol Spence. Errol said he'd found Kell so strong, so he knew he'd have to wait for the second half. A fighter who is tight and struggles at the weight is always weaker when it goes down the stretch and that's what happened. There was nothing in his tank, he was being bullied in the end."