Keane, 54, has been one of Carrick’s biggest doubters since the former midfielder was given the interim job at Man United.
Carrick has been a huge success, however, taking Man United back into the Champions League, and is set to be named the permanent manager.
Despite all that, Keane believes there are "still huge problems" at the club and that the real work is only beginning.
Speaking on Sky Sports after United's 3-2 win over Nottingham Forest, he said: “Yeah, he’s been in the driving seat the last few months,” Keane said when asked if Carrick deserves the permanent job.
“I’m guessing the remit for him was to get in the Champions League, they’ve done that but there’s still huge problems ahead.
“Was he still the best option out there? We obviously don’t know what other managers they spoke to. But the fact he was winning football matches… but still huge problems at United. Huge problems.”