Former UFC heavyweight champions Junior Dos Santos and Francis Ngannou were once foes in the MMA cage, but the two of them are now very respectful of each other.

Dos Santos, who is very interested in crossover boxing matches, was very impressed with Ngannou's performance against WBC champion Tyson Fury last October in Saudi Arabia.

Ngannou, who entered the ring as a tremendous underdog in his pro boxing debut, dropped Fury in the third round and gave him a lot of trouble as the contest played out. 

After ten rounds of action, Fury came away with a close split decision win.

"I'm so happy for [Ngannou]," Dos Santos explained to TMZ.... "All the boxing guys are always talking, saying on the striking side we are not able to go there and put on a good performance against them."

"Francis Ngannou was fighting probably the biggest heavyweight in the history [of boxing, someone] who never lost a fight," Dos Santos explained, adding, "and he did what he did. I was there. That was so amazing to see that. And, it showed what kind of work we [MMA fighters] do."

Ngannou blasted out Dos Santos in one round, when they met in the UFC in June 2019.

Dos Santos would love to face him in a rematch - in the boxing ring.

"That would be amazing, too! I think actually that would be something very good, not just for me, but for him, as well," Dos Santos said.

Ngannou will have his second professional fight on March 8, once again in Saudi Arabia, where he faces former two-time heavyweight champion Anthony Joshua. And once again, Ngannou will enter the ring as a massive underdog with the oddsmakers.