Anthony Joshua will be ringside when Dillian Whyte faces Dereck Chisora on December 22 – with the winner expected to land a shot at the unified heavyweight champion in April.
Joshua returns to the ring at Wembley Stadium on April 13, with his opponent yet to be confirmed.
Promoter Eddie Hearn insists fights with WBC king Deontay Wilder and Tyson Fury remain his No 1 and No 2 choices to be in the opposite corner.
But with Wilder and Fury set for a rematch early next year, the winner of Whyte-Chisora is the front-runner to face the WBA, IBF and WBO champion.
And Joshua will be among those watching at the O2 Arena, with Hearn also confirming on Monday that undisputed cruiserweight king Oleksandr Usyk and unbeaten American Jarrell Miller will be there.
“If we get Wilder, who is our No 1 choice, fantastic. If we get Fury, who is our No 2 choice, brilliant.
“If we don’t get Wilder or Fury, the winner of December 22 is a must, you have to say the winner of Whyte-Chisora is the No 4 heavyweight in the world…”
Hearn also claimed Chisora is one of AJ’s heroes from his early days as an amateur at Finchley ABC.
The promoter said Joshua used to label Chisora a “god” who showed him the way to “make it”.
Chisora and Whyte collide almost two years to the day since they shared 12 gruelling rounds of action in Manchester, with Whyte securing a controversial split decision win that laid the foundations for this month’s rematch.