Stoke winger Luke Chadwick is to seek medical help in an attempt to overcome his lack of stamina.
The former Manchester United man collapsed from dehydration during Stoke's opening day defeat at Southend.
Since then he has not managed to complete any of the Potters' six Championship games, with boss Tony Pulis substituting him in the second half on each occasion.
Pulis cannot understand why he keeps struggling in the later stages of games, but is determined to get to the bottom of the matter.
"He's going to have a chat with the doctor to see why he's feeling this way," Pulis told The Sentinel.
"He does so well for a period of time, but then tires. For an hour the other night at Sheffield Wednesday he was smashing. His first half movement and directness was causing them all kinds of trouble."
"The one thing we can be sure about is the fact it's not a question of attitude.
"Luke is a smashing lad, he really is, and a top pro."