Alan Shearer will see a specialist next week after suffering a recurrence of the knee injury which forced him to have an operation.
Shearer, who made his comeback from injury in the home defeat against Manchester City, broke down in training on Saturday.
Shearer's latest injury setback has raised fears that he could miss the remainder of the season.
"There was a reaction to the knee which was operated on a few months back," said Shearer.
"I came off straight away as a precaution and will be seeing a specialist next week," he said.
The timing is another blow for boss Bobby Robson, especially with £7m signing Carl Cort expected to be back in first-team action soon following hamstring surgery.
Robson was hopeful that the former Wimbledon frontman could link up with Shearer as part of a £22m strikeforce.