Paul Clement believes Renato Sanches is struggling with low confidence and not "getting simple things right" after he replaced the midfielder 45 minutes into Swansea's 1-0 defeat to Chelsea.
Sanches has made eight appearances for the Swans since joining on loan from Bayern Munich in August, but he has failed to make a positive impression in the Premier League, with Swansea lacking a victory in their last six games.
The 20-year-old Portuguese was substituted for Leroy Fer with Swansea and Chelsea goalless at the start of the second half, and Clement said the change was due to form rather than fitness.
"He wasn't injured," Clement told reporters. "He had a poor half, didn't he?
"I feel for him because he's a very talented player. I don't think in any of the games he's played this year he's showed the talent he has.
"He's a player struggling for confidence, struggling for form. We believe we're the right environment to try to get him out of that."
Sanches' struggle for form predates his spell at Swansea; he endured a torrid season in 2016-17, failing to register a goal or an assist in 25 games across all competitions for Bayern.
Just 18 months ago, the former Benfica star was named Young Player of the Tournament at Euro 2016 as Portugal won the competition for the first time in their history, but Clement said he needs to work on the fundamentals of his game.
"He's got to start with the basics, getting the simple things right," said Clement.
"He mis-placed a lot of simple passes. His confidence is very low.
"He wants it badly. It's just not happening for him in games at the moment."