Can you name fighters who seemed to have lost it after winning a tough fight?

[generalbulldog]

Gabriel Ruelas after fighting Jimmy Garcia. Garcia's death haunted him for the rest of his career. He was never the same mentally after that fight.

[JuliusHicks82]

First names that come to mind are Oliver McCall (after beating Lennox) and Hasim Rahman (after beating Lennox).

Probably a case of neither guy being that great to begin with, but after they found that sweet spot on Lewis' jaw, never truly capitalized on the momentum. McCall beat 87-year-old Larry Holmes in his one successful title defense, then lost to Frank Bruno. Rahman got waxed y Lewis in the rematch, then had the "other head on my head" fight with Evander, and kind of faded from view until he fought James Toney.

Courtney Burton after beating Angel Manfredy. He went 2-5 after that fight, getting knocked out five times. (Manfredy, for that matter, only fought twice after Burton.)

[holmcall]

Joe Mesi after "beating" Jirov.

[Master]

Frazier lost some of his mojo after the first fight with Ali. He did fight on well after, including the brutal third fight however.

[Hulk]

Zab Judah after knocking out Spinks in the rematch.

He never has looked that good again, at least not against good competition.