Newcastle United's first defeat of their Champions League return could prove an expensive one with injuries adding to manager Eddie Howe's frustrations after a 1-0 loss to Borussia Dortmund at a rainy St James' Park on Wednesday.
Defeat means Newcastle face a fight to progress from Group F although they are still well-placed with four points from three games, the same as Dortmund.
With games coming thick and fast, Howe said his squad could become stretched.
"Isak going off was a blow and Jacob came off with what looks like a serious injury," Howe said. "We've got a small squad as is it. That's probably the most disappointing thing of the night.
"It looks like a recurrence of his [Isak's] groin problem and it's a big blow. Jacob looks serious, potentially a dislocation of his shoulder."
Howe also confirmed that midfielder Elliot Anderson missed the game because of injury.
"He's got a back problem so I think he's going to be missing a number of weeks," he said.