Borussia Dortmund manager Lucien Favre has told Jadon Sancho only hard work will get him to the top of the game.
Sancho, 18, has burst into the spotlight this season as his form for Dortmund earned him an England call-up before Christmas and he has scored nine goals and provided 14 assists in 31 games.
But he has suffered from inconsistency in recent weeks as Favre's side have had a wobble at the top of the Bundesliga, seeing their seven-point lead over Bayern Munich wiped out.
Dortmund's Champions League campaign has also gone south as they trail Tottenham 3-0 going into the second leg of their last-16 tie on Tuesday and the German side will need Sancho to be at his thrilling best.
The teenager has all of the tools, says Favre, but must now apply himself.
"Jadon is a very talented player, he is 18 years old and sometimes at 18 it is up and down," Favre said at his pre-match press conference at Signal Iduna Park.
"He has played really, really well in the first half of the season and also at the beginning of the second half of the season, but sometimes he has some highs and lows.
"He has a lot to learn, he has a lot of potential and that is good for us. He has talent, but there is no talent without hard work. Talent is 10 per cent, hard work is 90 per cent."
Favre is in no doubt about the size of the task his side face against Spurs on Tuesday night after their second-half collapse at Wembley three weeks ago.
Dortmund were the better side in the first half at the national stadium but were swept aside after the break, with Son Heung-min, Jan Vertonghen and Fernando Llorente goals swinging the tie in the Premier League side's favour.
BVB have scored three or more goals at home on 12 occasions in all competitions this season and must do so again, without conceding, to have any chance of progressing.
"We know it will be very difficult but you never know," Favre added. "We have already played many games in this stadium where we have written history and we are in a position to achieve the impossible.
"We have to be clever, we have to reach our total peak and we have to score the goals at the right moment.
"If they score it will be very difficult, but the whole team believes in themselves.
"We have to give a top performance, it is very difficult but nothing is impossible.
"We know we can score goals but we have to be very clever with the way we play. We have to be careful with how we attack."
