Ivorian Salomon Kalou has told Chelsea he wants a guarantee of more game time before he signs a new contract at Stamford Bridge.
Kalou, 26, had looked set to leave the club when his current deal expires at the end of the season.
But manager Andre Villas-Boas revealed last week that talks had begun with the striker over an extension.
The parties need to reach an agreement before January if Chelsea are to avoid risking Kalou leaving for nothing.
Kalou scored after coming on as a second-half substitute in Wednesday night's 5-0 home thrashing of Genk in the Champions League.
But the Ivory Coast international wants assurances that he will be elevated from the fringe status he has endured since joining the club five years ago.
"That's what every player wants to have, game time," said Kalou.
"Because if you're not playing every weekend, how are you going to improve yourself?
"So it's very important to play to improve and to push yourself to the limit. That's what I'm looking for."
Despite playing in both the Carling Cup and as a substitute in the Champions League on two occasions, Kalou has failed to play a minute of Premier League football since 20 August.
On that day, he was substituted after just 35 minutes of the 2-1 home win over West Bromwich Albion.
Since then, he has failed to make the squad or twice been an unused substitute for Chelsea's Premier League matches.