Ray Wilkins says Diego Costa is key to Chelsea's title bid - but warned head coach Antonio Conte he must sign another striker in January.
After a difficult start under Conte, Chelsea have hit their stride in recent weeks with come-from-behind victories over title rivals Tottenham and Manchester City.
Costa has been one of Chelsea's star performers with 11 league goals this season, but reserve striker Michy Batshuayi has found the net just three times since his £33m transfer from Marseille.
Eden Hazard celebrate scoring against Man United with Costa (right)
Wilkins told Premier League Daily: "Chelsea's squad is very strong right across the board, but you would concede that they are so reliant on the forward areas and what I would say is that they do not have another recognised centre forward other than Diego Costa.
"They can play with all these smaller guys and play Hazard through the middle and Michy Batshuayi has come for £30m and we haven't really seen him yet. Of course, there are lots of youngsters out on loan which is another issue. But if they were to lose Costa that would be a massive, massive blow. But I still feel Chelsea have the most solid, resilient squad.
"They have the experience in there of players who have won titles, big game players if you like, and that is another key factor for them.
"For the last six or seven years it has been the same with Arsenal. They go up to Christmas and they look like world beaters and then after the holidays they have a nose dive. They can't seem to go the distance."
Chelsea have surged to the top of the table on the back of an eight-match winning run, with Costa helping himself to six goals, but Wilkins says he cannot carry the scoring burden alone.
He said: "They need another centre forward for sure and they should try and rectify that during the window, but the fact that they have not got European football is also a big factor in their favour no question about that.
"I was out at Cobham (Chelsea training ground) on Tuesday and Gary Cahill was having a coffee saying 'I've got a day off Ray.' The other players with the big guns can't have a day off, they are seven days a week now."
