Bakayoko, 24, joined the Blues a year ago by Antonio Conte in a £35m deal but he failed to make an impression at Stamford Bridge.
Although he did start the final four games of last season, including the FA Cup final win over Manchester United, a chance after Conte's exit was not forthcoming.
Maurizio Sarri instantly deemed the former AS Monaco star surplus to requirements and sanctioned his loan move to AC Milan with the Italian giants having the option to make the deal permanent at the end of the current season.
And his former midfield partner Fabinho, who was an integral part of the Ligue 1 title success and UEFA Champions League semi-final run in the 2016/17 season - claims the London based side could regret the decision.
"I don't think he struggled that much," the Brazil international told Yahoo. "I watched a few games and he seemed always good to me.
"Obviously, in your first season in a new club it’s always difficult and I wasn't expecting him to leave, but AC Milan are getting a great player.
"I'm sure he'll be able to prove how good he is and show what he did at Monaco.
"I'm sure if he comes back to England he will be stronger and will show everyone what he's capable of."