"I think it is bad news, what the doctor told me is not a good thing. It looks a bad injury so we will assess in the next days and we will see the period he is going to be absent from the squad," Pochettino told reporters ahead of Chelsea's visit to Craven Cottage to face Fulham on Monday.
"We are really sad about the news about Ben. The time(scale) is difficult to say now. The doctor will tell us and the club will communicate."
The Argentine manager is more optimistic regarding some other injury concerns. Carney Chukwuemeka (19) has not played since August 20th with a knee injury, but returned to training this week.
"I hope that maybe Carney, and of course Noni (Madueke) also, after his issue when he came back from the national team, he's getting ready.
"I hope that these two players will maybe be available for selection on Monday."
Chelsea, with just one league win from six games, have also failed to score in their last three Premier League games, with just five league goals so far this season.
Nicolas Jackson (22) scored the only goal of the game against Brighton, but the player, who also scored Chelsea's last league goal back in August, is unavailable for the trip to Fulham because of suspension.
The Argentine manager will need to plan for the next game without Jackson, as he looks to find a solution to his side's lack of goals.
"We have a few options, to play with a striker and without a striker. We need to assess the whole squad after the game, things appear after 48 hours and we need to see how they are and how they recover from Wednesday," he said.
"The most important thing is to adapt, the squad needs to find a way to perform, that is the most important."
Chelsea are in 14th place in the table with five points, with Fulham three points ahead in 11th.
