Aldo (17-2) injured his rib during training last week but says he still intends fighting McGregor (17-2) at the MGM Grand Garden Arena, even though UFC featherweight Chad Mendes (19-2) is on standby to replace him.
The injury to the champion now has McGregor as the favourite to win the bout from the seven time defending champion.
If Aldo can’t fight and is replaced by Mendes then McGregor will be the underdog according to the bookies, despite Mendes accepting the fight on short notice.
Nick Kalikas of MMAOddsBreaker.com has Mendes as a minus-130 favourite if the fight happens and McGregor is listed at plus-100.
"If Chad Mendes does indeed replace Jose Aldo for an interim UFC featherweight title fight, it's a drastic stylistic change for McGregor to deal with," Kalikas said.
"Aldo vs. McGregor is a traditional striker vs. striker matchup – but with Mendes, the threat of the takedown will be ever-present, as well as his tremendous striking power. The biggest question mark for this matchup is whether or not McGregor can stop the takedown from an elite wrestler.
"The popularity of McGregor is not something to be underestimated. He was getting a ton of respect from bettors even before the rumoured injury to Aldo. That being said, there are a lot of people who think Mendes is a bad stylistic matchup for McGregor.
“Until McGregor can prove he can stop the takedowns from an elite wrestler, he'll have to be an underdog," he added.