Swansea manager Graham Potter says Daniel James is Premier League class.
The midfielder is being linked with Manchester City.
"It is not for me to announce values and prices," Potter said. "(But) against Manchester City (in the FA Cup in March) he matches the physicality of Kyle Walker, for example, and runs away from players at that level.
"That's a direct comparison against Premier League players at the very top and you can see his quality.
"He plays alongside Gareth Bale (for Wales) and doesn't look out of place.
"You look at his attributes and how he influences games at Championship level. He causes teams real, real problems.
"It's up to the market to decide the rest, but I'm happy to have him with me and long may it continue."