Manchester United’s left-back Luke Shaw will be out for a number of weeks with a muscle injury that is still being assessed.

The 28-year-old defender is a mainstay of Erik ten Hag’s side and started the first two Premier League matches of the season. But Shaw will miss Saturday’s Old Trafford encounter against Nottingham Forest and next weekend’s trip to Arsenal as well, it seems, as England’s upcoming internationals.

A club statement read: “Manchester United defender Luke Shaw has sustained an injury which will rule him out of forthcoming games. The muscle issue is still being assessed but the England left-back is expected to be out of action for a number of weeks.”

United and England will be hoping nothing worse crops up during those assessments, especially with fellow left-back Tyrell Malacia also sidelined through injury. The Old Trafford club loaned out another left-back earlier on Thursday, with Brandon Williams joining Ipswich for the remainder of the campaign.

United had already announced an injury to Mason Mount ahead of the Forest match and it remains unclear whether the new signing Rasmus Højlund will be fit to make his debut. Amad Diallo, Kobbie Mainoo and Tom Heaton are also out, while Harry Maguire missed the trip to Spurs with a knock.

Mykhailo Mudryk is the latest addition to a long list of injuries at Chelsea after the Ukrainian forward sustained an injury in training. Chelsea have been hit with several injury problems early in the season, including their captain, Reece James, who suffered a hamstring injury on the opening day, and Christopher Nkunku, who has had knee surgery and is not expected to return until November.

Mudryk, who cost Chelsea an initial £62m in January, is the ninth player to be sidelined. The club have not revealed the nature of his injury. “He won’t be available for tomorrow [against Luton],” Mauricio Pochettino said. “It’s not a big issue. We need to wait one week or maybe a few days.”

Carney Chukwuemeka went off injured having scored in the 3-1 loss at West Ham on Sunday and the 19-year-old underwent knee surgery, but the recovery time should be shorter than first feared. “It is not an issue for months, maybe weeks,” Pochettino said. “It is a bit unlucky in some issues like with Carney on Sunday. That is football. A little bit unlucky with many of the injuries, but I am positive.”

Mykhailo Mudryk suffered a training injury to compound an indifferent start to the season

Mykhailo Mudryk suffered a training injury to compound an indifferent start to the season. Photograph: Jacques Feeney/Offside/Getty Images

The injury list also includes Wesley Fofana, Armando Broja and Benoît Badiashile. “Nkunku and Carney or Fofana. How can you control? It’s not about training or methodology. It sometimes happens,” the Argentinian explained.

“In some others, many factors can influence. It’s tough to talk in general because situations are different. You can talk about bad luck or bad training session. For sure, it is bad luck in Carney, Broja, Fofana, Nkunku.”

Pochettino spoke about the possibility of new signings: “We need at least one keeper. We have very talented young keepers but they need time. We were talking about one offensive player. If we can add the right profile, yes, but not to bring players so we can add more and to stop the evolution of some young guys.”

There was some good news for Chelsea as the British record signing, Moisés Caicedo, could make his first start for the club, having made a mistake for West Ham’s third goal on Sunday, a penalty decisive in their defeat. But fellow midfielder Roméo Lavia, who was signed from Southampton, may need to wait. “Mo [Caicedo] is ready to start. Lavia no. He needs a few weeks to be ready to be involved with the team,” Pochettino said.