Floyd Mayweather took time out from his training to remind Conor McGregor of his defeat three years ago.
Mayweather earned around €230million from his 10th-round stoppage of the UFC star in their crossover fight in Las Vegas.
It took his record to 50-0 and the ring legend bowed out from the sport following his one-sided victory.
The 43-year-old has since turned his hand to coaching in tribute to his late uncle Roger with a return to competitive action unlikely.
But during an Instagram live training session, Mayweather raised the possibility of a second clash with McGregor.
"Where he (McGregor) at? He don't want this," he said.
McGregor has long insisted he under-performed against Mayweather and intends to return to the ring.
The Dubliner stopped Donald Cerrone inside 40 seconds in January and had planned to fight three times this year.
One possible opponent is Manny Pacquiao who has signed with McGregor's management team.
The Filipino was pencilled in to fight Mikey Garcia in July but all boxing has been suspended due to the coronavirus crisis.
The UFC returns this weekend with a behind-closed-doors show headlined by Tony Ferguson's clash with Khabib Nurmagomedov.
The promotion will hold three events in the space of eight days in May as they bid to return to a normal schedule.
Boxing in the UK will likely return in July - also with no crowds - but a lack of gate receipts means many pay-per-view fights will remain postponed indefinitely.
Dillian Whyte vs Alexander Povetkin will be one of the first shows and is expected to take place in late July.
