QPR’s Darnell Furlong faces three months on the sidelines with the knee injury he suffered against AFC Wimbledon at the weekend.
Assistant manager John Eustace played down the significance of the injury immediately after Saturday’s pre-season friendly.
But West London Sport subsequently revealed that the problem was causing concern and that Furlong was facing another spell on the sidelines.
The defender, 22, missed almost three months of last season because of a knee problem.
Rangers confirmed on Thursday morning that he has suffered a torn ligament and undergone surgery.
“This is a massive blow for Darnell personally, and for the team. He has looked great throughout pre-season and we are all gutted for him,” manager Steve McClaren told the club website.
“However, I know the sort of personality Darnell is and he will be doing everything in his power to come back fitter and stronger than ever.”