Lucien Favre indicated that he is looking for an improvement from Borussia Dortmund winger Jadon Sancho, who he said has "highs and lows".
Borussia Dortmund's Jadon Sancho has "a lot to learn" according to head coach Lucien Favre, who called for the 18-year-old to focus on his work rate to fulfil his potential.
Sancho has scored eight Bundesliga goals in 24 appearances for Favre's table-topping side this season but was on the receiving end of criticism aimed at the whole team after Dortmund were beaten 2-1 at Augsburg on Friday.
Former defender Matthias Sammer described BVB as "immature" following the result, and Favre admitted that Sancho's outstanding performances this season have not come with consistency.
"He's a very good player, a very talented player," Favre told reporters ahead of Dortmund's Champions League last-1616 second-leg clash with Tottenham.
"He's 18 and sometimes with 18 it's up and down.
"He had played really, really well in the first half of the season and at the start of second half but he has highs and lows.
"He has a lot to learn, a lot of potential. But for every player who has talent there is no talent without hard work.
"Hard work is 90 per cent. Talent is 10 per cent."
Dortmund go into their clash with Tottenham trailing 3-0 after a first-leg defeat at Wembley, and no side has ever won a Champions League knockout tie after losing the first leg away from home by that scoreline.
Favre played down the impact of Sammer's comments about his side, who are only ahead of second-placed Bayern Munich in the Bundesliga table on goal difference.
"I have often spoken to Matthias at the beginning of the season and since," said Favre. "We have a good understanding. But he is a journalist in those situations and we are a democracy. Everyone can have his opinion.
"I have every trust in him. On TV he has a right to say what he can say. It's not a problem for me. But I did not see the show. So I can't really judge this."