Isaac Success will spend some more time on the sidelines after Watford manager Walter Mazzari confirmed the Nigerian forward suffered a relapse, ahead of their Premier League clash against Swansea on Saturday.
Success produced a man-of-the-match performance at Middlesbrough last weekend, but Mazzari added that he had been struggling with a "muscular problem" that has once again flared up.
"I subbed him [last week] because the physio was telling me he was hurting. I tried to keep him on for as long as possible during the game but after 90 minutes they looked at him and said he would not train due to a muscular problem," Mazzari said.
"Even in the past I have been saying he has not been training regular because of his muscle problems.
"He has been having problems in the upper right leg. He didn't train all week so he is also a doubt for Saturday's game at Swansea. He may not be available.
"I don't look at how my players played in the last game but look at how they trained all week."
The 20-year-old Success has started once and came off the bench on six occasions for the Hornets this season, scoring one goal in the process.