Manchester City manager Pep Guardiola urged Leroy Sane to respond after the attacker's slow start to the season.
Sane, 22, starred last campaign, winning the PFA Young Player of the Year award as City cruised to the title, but he is yet to start a Premier League game in 2018-19.
He was left out of Germany's World Cup squad in Russia, while his body language was questioned by team-mate Toni Kroos during the international break.
Guardiola called for Sane – who has played just 30 minutes in the league this season – to bounce back, but said it was too early to judge the former Schalke attacker.
A challenge for Sane
"He will be so important for the club. It's a challenge for him and not just him – everybody," Guardiola told a news conference ahead of City's clash against Fulham.
"The season will be judged in 11 months – not three weeks. He's a nice guy and I don't have any bad words about him.
"He has to respond in the right way. He's so competitive and professional. Sometimes, for some players, it's that way [a slow start]. Some players at the end of the season go down.
"We cannot forget he is 22 years old. Bernardo Silva, Gabriel Jesus, Raz [Raheem Sterling] – the other ones are young – and he will grow up. The most important thing is to try to help him."
Sane, who joined City in 2016, finished last season with 10 goals and 15 assists in the league.
Guardiola said he was still keen to work with Sane, but said the likes of Silva – who made just 15 league starts last season – also deserved their chance.
"Bernardo Silva started in incredible condition and he deserved to play; Raz is playing well," he said.
"It's a challenge for all of them and a challenge for me and them is to keep that level.
"Everybody is here because after three seasons, I want to work with them. It's simple like that."