Anthony Joshua should call time on his boxing career if he loses to Jermaine Franklin next weekend, according to former WBO cruiserweight world champion Johnny Nelson.
Two-time heavyweight champion Joshua has fallen down the pecking order for another shot at the belt after losing back-to-back fights to Oleksandr Usyk.
The 33-year-old has tasted defeat in three of his past five bouts, with Andy Ruiz Jr sensationally ending his opponent's unbeaten streak of 22 fights in June 2019.
Joshua returns to action on home soil at London's 02 Arena on Saturday in what will be his first fight since 2015 that has not been contested with a world title on the line.
And Nelson believes Joshua's career will effectively be over if he loses to Franklin, whose run of 21 wins in a row was ended by Dillian Whyte in November.
"If Anthony Joshua loses, he jacks it in," Nelson wrote in his column for Sky Sports. "If he doesn't jack it, he should jack it. Because it's a hard mountain to climb.
"Especially when you've had the success and the heights that he's had. So he can't afford to lose. That's a must. Then from that, it's confidence building.
"We'll see if he really thinks 'you know what, I can eventually become world champion again, I'll fix what I got wrong'. He's only been boxing 10, 11 years as a professional fighter."
A showdown between Joshua and Tyson Fury twice fell through, but there has been renewed talk over the past week of the two men facing off later this year.
However, given the similar nature of Fury's proposed bout with Usyk also collapsing, Nelson is no longer interested in discussing that all-British clash.
"Personally, I fell in love with the idea at first but it was teased so much and it never happened," he said. "So I don't even don't want to talk about it."