American super-middleweight Douglin, 32, recently revealed how Mayweather called him up at 1am to request an off-the-cuff sparring session at his Las Vegas gym.
And after going toe-to-toe with him in Sin City, ‘Momma’s Boy’ believes the former five-division world champion could still compete with the young champions of today.
Mayweather has not fought competitively since his stoppage victory over UFC superstar McGregor in August 2017, which went down as the second highest-grossing boxing event in history.
McGregor, who defied the pre-fight odds by going 10 rounds with the boxing great, is desperate to lure him back into the ring for a rematch.
Yet Mayweather is not short of options, as UFC Lightweight champion Nurmagomedov is also eager to land his own crossover bout with the 43-year-old.
Douglin believes it is “very possible” that we will see Mayweather return for a showdown with either McGregor or Nurmagomedov, suggesting he was only brought in to spar with him for that very reason.
When asked about Mayweather potentially facing one of the two UFC stars, he said via Vegas Insider : “I do think this could happen, I think he's going to fight UFC guys.
“It’s actually quite interesting because I'm left-handed and McGregor and Khabib are both left-handed, so him choosing to spar me, that might be the reason why.
“That's something someone said to me the other day and I was like, you know what, that makes sense, so it’s very possible.
“The Conor McGregor fight generated so much money, why not do something like that again or fight another UFC fighter if he's making millions of dollars?”
Mayweather clearly hasn’t lost any of his unparalleled work ethic, as Douglin also revealed that the pair slugged it out in a brutal 30-minute round of sparring.