Liverpool forward Diogo Jota will miss the World Cup after being ruled out for months with a calf injury.
The Portugal international was carried off on a stretcher late on in Sunday's 1-0 English Premier League victory over Manchester City.
"It's really not good news about Diogo. Yes, he will miss the World Cup," said Jurgen Klopp.
"(It’s a) pretty serious injury in the calf muscle and now the recovery process starts. That’s it pretty much.
"That is the first diagnosis, which was pretty clear, and all the rest will now follow in the next few days.
"It is very sad news for the boy, and for us as well of course for Portugal. But no (he doesn’t need an operation).
"(It will have a) big impact. So, now we can say that because he will not be in for a long time; we talk about months.
"So, we will see. I don’t want to put now a number on it because I always hope in the middle of the rehab there is a very positive development and we can cut days off the rehab phase, but it will be long."
Jota expressed his disappointment in a post on Twitter.
"After such a good night at Anfield mine ended in the worst way! In the last minute one of my dreams collapsed," he wrote.
"I will be one more supporting from the outside, club and country, and fighting to be back as soon as possible. You’ll Never Walk Alone."
Later on Tuesday, Chelsea confirmed that France N'Golo Kante has also been ruled out of the World Cup after undergoing an operation on his hamstring which will see him sidelined for four months.
The 31-year-old suffered the injury in Chelsea’s 2-2 draw with Tottenham back on 14 August and had surgery after suffering a setback in his rehabilitation.
A Chelsea statement said: "N’Golo Kante has undergone an operation on his hamstring injury.
"The midfielder visited a specialist with the club’s medical department to explore the options for his rehabilitation approach and it was mutually agreed for N’Golo to have surgery to repair the damage.
"Following a successful operation, N’Golo is now expected to be sidelined for four months."
The decision to have surgery came after Chelsea boss Graham Potter, who has been unable to call upon Kante since taking charge at Stamford Bridge, admitted last week there were long-term concerns over the midfielder’s fitness record – he has missed 57 games since the 2019 Europa League final.
"Historically, there are things which have happened which are a concern, and we need to get the bottom of that," Potter said.
"It’s a setback in the last stage of his rehab, so again that’s worrying. But all we can do is get the right diagnosis, the right consultation and then try and help him get back to full fitness and enjoying his football."
Kante, whose Chelsea contract expires next summer, has 53 caps for France and was part of their World Cup-winning squad in 2018.
Confirmation of Kante’s diagnosis comes two days after Chelsea team-mate and England right-back Reece James was ruled out for up to eight weeks with a knee problem, meaning he too stands to miss the World Cup which kicks off in Qatar on 20 November.
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