Clayton is training with Wolves after a fortnight with Sunderland.
"He's been at Crewe for a long time and through my previous job as academy manager and Stuart Webber's previous background as head of recruitment at Liverpool's academy, he's a player we've all been aware of for a long time and been tracking," Thelwell told The Sentinel.
"Before he got his ankle injury, I'm sure he was set to follow Nick Powell into a Premier League club really.
"There was some solid interest from Manchester United among others.
"But his situation has changed; he got a bad injury to his ankle which meant he was available for us to trial.
"And because he was a player we know so well, it seemed a bit of a no-brainer to get him in for a few days.
"That's where we are at the moment - he's been in for two days.
"It's early days in terms of where we are with him and where he is with us."
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