Chelsea manager Mauricio Pochettino is hoping Wesley Fofana will be back before the end of the season after his massive ACL injury blow.
The new Blues boss was speaking just hours after the $70million defender underwent anterior cruciate ligament reconstruction.
'I hope he can be ready to play this season,' Pochettino said in his press conference on Tuesday ahead of the club's first pre-season friendly on their US tour.
'We know very well it is difficult. Different bodies, different physiological people. He is evolving in a different way.
'We hope everything is going well with his recovery and he can be ready.'
Chelsea confirmed Fofana had an operation in a statement on Tuesday. No timeframe on his likely return was given.
Fofana only joined the Blues last summer from Leicester with his first season hindered by a major knee problem.
In what was a difficult season for the whole team, the 22-year-old endured a frustrating campaign, playing just 15 times in the Premier League.
'It's really sad, really bad news. We feel all so so sad,' Pochettino added at The University of North Carolina in Chapel Hill.
'Only thing we can do is to help him and to be again with the team. We know it's tough. We need to help him, wish him the best and be again with the team.
'It is tough but we need to keep going. The competition does not wait for anybody and we need to be ready to compete.'
Fofana was not the only one left back in England as Romelu Lukaku, Pierre-Emerick Aubameyang, Hakim Ziyech and Callum Hudson-Odoi were not part of the travelling party.
The quartet's futures are all uncertain after falling down the pecking order following the arrival of Pochettino this summer.
Although the Argentine did not shed too much more light on whether they are close to departing.
'When this type of decision is because all agree. Player and club are working hard to try and find best solution.'
As Pochettino continues his massive overhaul of the squad following the club's woeful season, an inexperienced and threadbare side has jetted out to the States.
Thirteen players have left while work is ongoing to try to bring in fresh faces, including Brighton's Moises Caicedo.
'All the team are working really hard to try to earn what we want. I don't want to talk about specific names,' Pochettino said after the Seagulls rejected Chelsea's $70m offer.
Chelsea's travelling party features just six midfielders, who average only 7.6 Premier League starts each, but Pochettino called on his youngsters to take their chance and show what they can do.
'Tomorrow is going to be a good possibility to see the young guys, to show they are ready to play for a club like us. No pressure but they need to show us.'