Complacency crept in to James DeGale's IBF world super-middleweight title defence against Rogelio Medina, says Johnny Nelson.
The Londoner (23-1-KO14) retained his crown via a unanimous decision but at times seemed capable of forcing the stoppage and admitted in the aftermath he was disappointed in his performance.
With WBC champion Badou Jack bringing a unification bout between the pair closer by earning a majority draw with Lucian Bute on the same Washington bill, Nelson believes neither did themselves justice on the night and expects standards to rise for the showdown.
Nelson told Sky Sports: "We saw the skills that James has got, the speed and the unorthodox style. He made it look so easy at times and when he was slipping shots against the ropes, Medina didn't know what to do with him.
"Then on the other hand, because he was so busy looking good, he wasn't picking up the points or getting the job done. He did it in spurts and at times I thought he was gassing a little bit because when he turned it on, he'd do it for 15 seconds then switch it off.
"I think it was complacency because he knew he was head and shoulders above Medina. When you get into that mode of thinking you're too good, all of a sudden you're in deeper water than you realise. That's when it becomes a problem.
"There's frustration for [Jack's promoter] Floyd Mayweather and for Jack but Bute did a job at 36 years old. He came through, fought his corner and put up a decent performance.
"It's a good match. I think both fighters, Jack and DeGale, will perform completely different to how they did [against Bute and Medina]. Both fighters suffered the curse of that second defence where fighters either slip up or have a wake-up call.
"For DeGale and Jack, we'll see completely fighters next time when they fight each other."
Matthew Macklin, who worked alongside Nelson on the broadcast, believes the Briton will have the edge when the pair meet.
He added: "I think DeGale wins. I think he'll be a lot better next time. He under-performed and you could probably say the same thing for Jack a little bit as well. Both were probably looking past the fight at the unification fight.
"I think both will be better but I think DeGale is probably the better man."