Swedish pundit Stefan Schwarz has expressed concerns about Alexander Isak's fitness. The former Arsenal and Sunderland midfielder believes he could pose a challenge for Liverpool head coach Arne Slot this season.

Isak's £125m departure from Newcastle United was one of the most talked-about moves of the summer transfer window after he refused to pull on the Magpies' shirt again after accusing the club of "broken promises." The Sweden international had a string of injuries during his stint at Newcastle, with various groin and thigh problems sidelining him.

However, as reported earlier this season, Liverpool's medical and sports science team carried out a thorough examination of Isak's injury history. Only after being assured that his past injuries wouldn't be a problem did the club give the go-ahead for the deal.

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After missing pre-season, Isak was sidelined from the Liverpool squad due to a lack of fitness. His return was brief, as the striker experienced further discomfort in his groin.

Schwarz thinks this is the main concern for Slot. Speaking to Hajper, he said: "Alexander Isak is a fantastic player.

"The quality, the finishing, the movements, the intelligence on the pitch. He creates space for himself and others; the link-up play.

"But I believe there's one thing that worries me a little bit, it is his fitness. Every club that he's been to or played for, he hasn't been able to continue week in and week out; it isn't a new problem.

"That's probably the challenge Liverpool has - to get the best out of Isak. Because he's a tremendous player, and I believe we know when he's playing, he can do magical things.

"He has super finishing, and it's very difficult for the opponents to know where he is. He's so clever, intelligent.

"But for me, it's the fitness level. He has to play week in and week out to get that continuity to even improve and to get on a higher level."

Isak was on the pitch for 28 minutes during Sweden's World Cup qualifier against Switzerland on Saturday. He also started Tuesday's match versus Slovenia as a substitute.

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