Derby County striker Nathan Tyson's comeback from a niggling groin injury has been put on hold and he could be out until mid-November.
Tyson was pencilled in to play in a behind-closed-doors friendly against Chesterfield at Derby's Moor Farm training ground on Wednesday with a view to being named in the squad for the trip to Middlesbrough on Saturday.
However, the 29-year-old felt some discomfort in his groin during training and sat out the game as a precaution.
He could now be out until mid-November, when Championship action resumes after the international break.
The news is a further blow for the Rams, who have lost leading goalscorer Steve Davies for three months with a fractured skull.
Tyson has been plagued by a groin problem since joining Derby from East Midlands rivals Nottingham Forest in the summer.
He sustained the injury in the final pre-season friendly against Aston Villa and it has restricted him to only 24 minutes of action for the first team.
He came on as a 66th-minute substitute during the 2-1 victory against his former club at the City Ground last month.