The 28-year-old has struggled in front of goal, despite starting every Premier League game this season for Roberto Di Matteo's side, and may soon be replaced with Goal.com revealing the club have opened negotiations for Atletico Madrid forward Radamel Falcao.
|14/1||Fernando Torres is 14/1 to be the top Premier League goalscorer with William Hill
And Gullit maintains it is "a mystery" as to why the striker cannot find the net regularly for Chelsea when he was so prolific for Atletico and Liverpool before his £50 million switch in 2011.
"[Chelsea] wanted to give Torres a chance. Has he taken it? I don't know," he told reporters.
"What he had done in the past at Liverpool and at Atletico was unbelievable. And he can't do it for some reason. I don't know why, I have no clue. It's a mystery.
"But if he can't do it then Chelsea need to do something else."
The forward scored 24 league goals for Liverpool in the 2007-08 season, but only hit six league goals in Chelsea's last campaign, although he contributed to the Blues' Champions League triumph, netting in their semi-final win over Barcelona.
However, Gullit believes it is unlikely the club will compete for the cup again this year, saying: "I think it was a surprise to win it last year.
"They've tried to change the way they play. But they have to work hard to get to the last stages.
"They are in a transition. Di Matteo has bought some players that can play a more attacking way, a more spectacular way, and they do occasionally.
"But it takes some time to adjust so there will be ups and downs."