We thought Errol Spence Jr. had all the makings to be great. The unbeaten welterweight did nothing to disprove that theory on Saturday.

In the biggest test of his young career, Spence traveled across the pond and captured Kell Brook's IBF welterweight title by 11th-round TKO in a thrilling test of high-speed chess at Bramall Lane in Sheffield, England.

Spence (22-0, 19 KOs) showcased skill and poise by trading at close range and pounding Brook (36-2, 25 KOs) into submission due to a badly swollen left eye. But more importantly, the native of Desoto, Texas, proved he had both a chin and a backbone to overcome an incredibly stiff challenge in enemy territory.

"[Brook] is a tricky fighter, he's awkward. He's very strong and he can punch," Spence said. "But I proved today that I have a chin and that I have true grit. It's a legacy-defining fight and that's what true champions do. You go anywhere to fight. He came to America and took the title, so I came over here to take the title from him."

Spence, 27, did nothing to suggest he doesn't posses the kind of potential to one day sit atop boxing's pound-for-pound list. The southpaw targeted the body throughout and outlanded Brook 246-136, according to CompuBox.

The bout was close throughout, featuring plenty of even rounds as both fighters routinely answered one another with powerful and accurate combinations from close range. Brook led on two of three scorecards at the midway point, but Spence began to come on and firmly establish himself after Round 8 when Brook, with his left eye beginning to swell, started to fade.

"I watched some of his fights and he liked to fight at a certain pace," Spence said. "But once you pick up the pace on him, he kind of breaks down a little bit and can't throw a lot of punches. I decided to press the action, make him fight at a pace he didn't want to fight at and he started breathing hard and slowing down. I knew that I had him."

After Spence capped a huge Round 9 by digging to the body, forcing Brook to circle away, the native of England began to completely unravel the following round. Or so it seemed.

Spence jumped all over Brook to open Round 10 and floored him following a series of combinations along the ropes. But after Brook regained his feet, the round turned into an all-out war. Brook dug deep as both fighters traded huge in the center of the ring over the final two minutes in a surefire round of the year candidate.

"I got hurt when I got put down but I got back up and fought," Brook said. "I'm a warrior."

"Definitely that was one of the best rounds," Spence said. "He showed that he was a true champion just like against [Gennady] Golovkin. He was hurt, he was tired, and he pushed it out. He came back firing shots. I came back firing shots, and it was an awesome 10th round."

The skirmish in Round 10 proved to be Brook's last stand. With Spence leading on all three scorecards (97-92, 96-93, 95-94) entering Round 11, the former U.S. Olympian closed the show in a big way by walking Brook down and forcing him to willingly take a knee before referee Howard Foster counted him out.

"I would say Spence is one of the best kids I have been in with, if not the best," said Brook, who made his first appearance since breaking his right orbital bone against middleweight champion Gennady Golovkin last September. "I got caught in about the seventh round in the eye and it felt the same as the Golovkin one. Probably not as bad as that time but I was getting hit in all of the rounds and it was getting worse.

"In the last round, he caught me, and it just stuck there with double vision. I couldn't see out of the eye now. I couldn't see, so I had to stop."

Forced to wait for Brook to recover from his eye surgery following the Golovkin loss, Spence entered the fight after the longest layoff of his career at nine months. In the end, it played a factor in his performance.

"I kind of give myself a B-minus. I don't think that I did too good," Spence said. "I was off on my offense and my defense. I give Kell a lot of credit. It didn't plan out exactly like I thought it would. I thought I would come out a little bit sharper, and I didn't feel all that sharp tonight. But as true champions do, they push it out and show true grit like I did."

Brook, 31, said after the fight he could make 147 pounds again if needed but that his future was likely at junior middleweight. His promoter, Eddie Hearn, shared interest in making an all-England showdown against Amir Khan at 154 pounds.

Spence, meanwhile, had no question about what he wants to do next after winning his first world title.

"The goal is to unify the titles," Spence said. "I want to fight Keith Thurman next, Manny Pacquiao next. I want to fight the champions, unify the division and become the undisputed champion of the world.

"I've been calling Keith Thurman out for a long time. Now it's time to fight."