That is the verdict of Sky Sports pundit and former Celtic and Scotland striker Alan McInally.
Chelsea’s two recognised strikers Alvaro Morata and Olivier Giroud have both struggled this season.
Morata has five goals in 14 Premier League appearances but is now set for a spell on the sidelines with a knee injury.
Meanwhile, Giroud has found the back of the net just once in the league.
Eden Hazard was used in a central role against Manchester City last weekend.
But McInally says Sarri must sign an out-and-out striker next month to give them the best chance of finishing above the likes of Tottenham and Arsenal.
“I think they have to (sign a striker),” McInally said.
“If we think they’re not going to win the title then to finish in the top four they’re going to have to spend money on a striker. Obviously Morata is injured.
“They’re so inconsistent Chelsea. You couldn’t guarantee they’re going to go to Brighton (on Sunday) and win, it’s one of them.
“They’ll be favourites to win the game but you don’t know what Chelsea is turning up.
“And if they want to finish in the top four, they’ll need to get someone who can put the ball in the net regularly.”
Morata, meanwhile, has been linked with a shock move to Barcelona.
But ESPN FC pundit Alejandro Moreno says the Spaniard would only be a backup option at the Nou Camp.
“Barcelona would be taking him at a discount,” Moreno said.
“It would have to be under his knowledge and acceptance of the fact that he’s going to be what he was at Real Madrid and what he was at Juventus, which is a second-choice striker.
“Maybe that’s his best role.”
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