The real reason Tony Ferguson won't fight Michael Johnson -- "He remembers the last time I whooped his ass!"
That's what the UFC fighter told us in Vegas moments ago when asked why he thought Ferguson wouldn't agree to let him replace Khabib Nurmagomedov this weekend at UFC 209.
As we previously reported, Dana White was down to let Johnson step in at the last minute -- but Ferguson said no.
Johnson admits he understands why Ferguson wouldn't want the bout -- "It's a risky fight for him" -- but says the dude needs to STOP DODGING HIM!
FYI, Johnson is the only UFC fighter to beat Ferguson ... woulda been a good fight.