Cole played alongside Eden Hazard in the final two years of his time at Chelsea.
He says the Belgian is one of the greatest players he has played with.
However, Cole admits Hazard was never the best trainer during non-match days.
“He’s got to be up there in the top three or four, what he can do on the ball,” Cole said of Hazard on Sky Sports.
“In training you wouldn’t think it, probably with his hands in his pockets and his laces undone.
“But when he gets on that pitch on a Saturday afternoon he’s electric.
“He can go left, he can go right, at times he’s unplayable, as we’ve seen in the season.
“He’s a big player for them and you need him to keep firing on all cylinders.”
Hazard is Chelsea’s top scorer in all competitions this season.
And Cole says it is important the forward stays fit to build a partnership with new loan signing Gonzalo Higuain.
“We know how big of a key player he is for Chelsea,” Cole said of his former team-mate.
“But I think with Higuain coming in I think they’re going to settle in well.
“He scored two great goals at the weekend.
“And yeah I think we need Hazard to be on top form in every game, which I don’t know is a good thing or a bad thing.
“I think we need more of the other players to step up their game.
“But yeah I think if Hazard gets injured it’s going to be difficult for Chelsea to keep fighting for that top four.”