New Aston Villa manager Alex McLeish wants injury-prone Fabian Delph to justify his £6million price tag.
The now-21-year-old moved to Villa Park in August 2009 with the reputation of a star in the making following his emergence at Leeds.
But Delph has suffered from a number of injuries and ahead of Villa's return to pre-season training on Friday he is currently recovering from an ankle problem.
McLeish, who took over earlier this summer after a controversial switch from derby rivals Birmingham, has consequently challenged the midfielder to fulfil his potential.
The Villa boss, who has lost Ashley Young to Manchester United, while Stewart Downing is a target of Liverpool, said: "I think it's time for Fabian Delph to show the reason why Villa invested a decent sum of money on a very young player.
"The challenge is there for Fabian. He can certainly tackle as well as pass the ball. He's got that quality.
"He's got a determined attitude and believes in himself."
McLeish will use pre-season to determine whether Delph is ready for the Premier League.
He said: "We'll get a good idea in pre-season and will assess him then. I have to assess if he is ready for the Premier League.
"But for him, after his injury problems, to get a full season would be a massive boost to his mental toughness."