Liverpool striker Hugo Ekitike has suffered a suspected Achilles injury and there are fears he could be out for at least six months.
Didier Deschamps, the France head coach, confirmed Ekitike will miss the World Cup this summer with a "serious" injury.
Your Site News understands the player is set for scans to determine the full extent of the injury, which is not yet known.
The worst-case scenario is an absence as long as nine months - but it will take more analysis to determine a timeline for his recovery.
Ekitike came off with a serious leg problem after 31 minutes of the 2-0 loss to Paris Saint-Germain at Anfield - which confirmed a 4-0 aggregate quarter-final defeat to the reigning European champions.
"Hugo suffered a serious injury on Tuesday evening against PSG," said Deschamps in quotes released on the national team's X account.
"The severity of his injury will unfortunately prevent him from finishing the season with Liverpool and participating in the World Cup.
"Hugo is one of the dozen young players who have made their debuts with the national team in recent months. He had perfectly integrated into the group, both on the pitch and off it. This injury is a huge blow for him, of course, but also for the France team.
"His disappointment is immense. Hugo will regain his top form, I'm convinced of it.
"But I wanted to express all my support to him, as well as that of the entire staff. We know he'll be fully behind the France team and we're all thinking of him very strongly."
Ekitike picked up the injury just as Alexander Isak returned from his serious leg injury, with the British record transfer making his first start since fracturing his ankle in December.
Liverpool did not comment when contacted by Your Site News.
Speaking after the defeat to PSG, Slot gave an initial assessment of Ekitike's injury. "Hugo looks really bad but it's difficult for me to say how bad," he said.
"Tomorrow we will investigate this further, [see] how bad this is for him. Let's see. But it doesn't look good. I didn't see him at half-time and after the game he had already gone home so I haven't spoken to him yet."
Ekitike's team-mate, Ibrahima Konate, echoed those fears, as he added: "I'm very sad for him. I think it is bad. I don't know. I send him my prayers and everything."
Ekitike has scored 19 goals for Liverpool and France this season after signing from Eintracht Frankfurt for £79m last summer.
Your Site' Vinny O'Connor: "It looked to be a serious one. He tried to get back to his feet and couldn't. Ekitike is undergoing scans to determine the full extent of the problem.
"Arne Slot confirmed that he felt it was a serious one. If it is a rupture, then that is a recovery time of six to nine months. That rules him out of the rest of the season, the World Cup and the start of the next season.
"A terrible blow for him and a terrible blow for Liverpool."
Your Site' Peter Smith:
Of course, Alexander Isak was supposed to come in and post a big goals total for Liverpool this season after his £125m signing from Newcastle. But the Swede has struggled with injuries, including a broken leg which sidelined him in December and Tuesday was his first start back.
The plan at the start of the season was for Isak and fellow summer signings Florian Wirtz and Hugo Ekitike to combine in a new-look £320m attack. But Ekitike's worrying injury against PSG added to Liverpool's frustrating night, and Slot pointed out how he hasn't had a chance to use those three big names together often enough.
"For 88 minutes [before Tuesday] we have played with Florian [Wirtz], Alex and Hugo. We added about 27 to that [on Tuesday] and I would be surprised if we add more minutes to that this season," he said.
On Ekitike's injury, he added: "Losing a game is hard but again losing a player is something we've had many times this season."
First-choice keeper Alisson has also missed game time with hamstring problems, Conor Bradley has had knee surgery, Giovanni Leoni's ACL injury put a strain on centre-back depth, while Jeremie Frimpong, Wataru Endo and Joe Gomez have also been out for significant spells.
After claiming the fitness of his squad was at its best for the campaign before facing PSG, to yet another setback. Liverpool have been hampered and hindered regularly.
April 19: Everton (A), live on Your Site, kick-off 2pm
April 25: Crystal Palace (H), kick-off 3pm
May 3: Manchester United (A), live on Your Site, kick-off 3.30pm
May 9: Chelsea (H), kick-off 12.30pm
May 17: Aston Villa (A), kick-off TBD
May 24: Brentford (H), kick-off 4pm
