Butler, a second half sub at Wolves on Tuesday will definitely be out for the weekend trip but should be back for the Watford game on Sunday week with Roberto not ready to take chances on an injury at this stage of the season.
Speaking to Wales Online, the Swans boss said โWe had bad news with Tom on Wednesday
โHe felt his hamstring slightly and he will be missing against Doncaster.
โWe canโt take any risks with that sort of injury. Itโs nothing serious or long-term though and he should be available for the Watford gameโ
Martinez also said that despite their first defeat in six on Tuesday, confidence in the camp remained high
โConfidence hasnโt been affected at all,โ he said.
โI think we can take a lot out of that performance.
โIf I had to lose again it would be the way we did against Wolves.
โThe way we passed the ball, kept control and defended all over the pitch was very impressive for a team that has only just been promoted.
โDoncaster will be a completely different kind of challenge and it will be a difficult place to go at this time.
โItโs going to be scrappy because they are fighting for every point.โ