Hull City boss Iain Dowie believes Jozy Altidore must work harder in training if he is to fulfil his potential.
The USA striker has headed back to Villarreal after scoring just once in his season-long loan with the soon-to-be relegated Tigers.
While Dowie believes the 20-year-old has great ability, the Tigers boss feels he needs to focus more on the training field and improve his 'football intelligence'.
Dowie said: "The fans have been fantastic, given him great support and probably he hasn't fulfilled his potential here. He's got one goal and for the level of investment it's probably not enough.
"I've spoken to Jozy a number of times since I've been here and, if Jozy can train the way he plays, I think he's got a great opportunity but he needs to understand that it's that day in, day out.
"He's a lovely, laid-back boy and there's no side to him but he needs to focus on training at a better level.
"Kevin Kilbane keeps turning it out because he trains at that level, Nicky Barmby can keep playing because he trains at that level.
"It's a different level than Jozy's used to training at and he's got to get used to it. He found the physicality of the Premier League very hard when he came in. He's got used to that now but he must not get comfortable.
"You've got to stretch yourself every day in training. I said that to him and wished him all the best for the World Cup. I wouldn't be surprised if he had a good World Cup.
"He's got the right attributes if he can play to his strengths, and that is turning defenders and running at goal. He's a monster of an athlete but he's got to use that physicality, it's about imposing that.
"I've always felt the best part of a player's make-up is the two yards in his head. The (Teddy) Sheringhams, the (Alan) Shearers, the (Paul) Scholes, the (Ryan) Giggs, the (Wayne) Rooneys are two yards ahead of you in their head.
"Their football intelligence is bright and I think that's also something probably Jozy needs to work on."
Big expectations followed the 20-year-old to the KC Stadium but his Hull career ended on a low note when he was sent off for headbutting Sunderland's Alan Hutton last weekend.
The three-match ban meant an early end to his loan spell and, with the Tigers' relegation to the Championship all but confirmed, there is no chance of the club spending the £6million it would take to make the move permanent.
Altidore apologised to the Hull fans for his red card earlier this week, saying on Twitter: "I'm so sorry. Made a stupid, immature and costly mistake. I apologise to Hull City and the fans who I let down.
"I let my emotions get the best of me and lost my composure. Believe it or not, this year playing for Hull was to date the best trip I've ever been on."