Pep Guardiola says Manchester City striker Sergio Aguero must show he "deserves to continue here" before earning a new contract, with his deal set to expire at the end of the season.
Aguero, City's all-time leading scorer, played for just over an hour in Saturday's 1-0 home win over Arsenal in the Premier League as he returned after four months out with a knee injury.
Guardiola is convinced Aguero will be able to rediscover his usual prolific goalscoring form, but the City manager has warned the 32-year-old Argentina international his future at the club is not guaranteed.
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"Sergio now has to show, like every one of us, that he deserves to continue here - keep playing well, scoring goals and winning games - and after that the club and I will decide," Guardiola said of Aguero, who is free to speak to foreign clubs from January.
"But if he is playing in his level we don't have any doubts that he is a player to stay until he decides because he is unique. He is important for us, our fans and everyone.
"But he was out four months and he has to start training regularly and start to score goals - this is the most important thing.
"Having Aguero on the pitch, we are better, we are safer. We missed him a lot in the important moments at the end part of last season, but now is good news for us that he is back."
Guardiola also played down an incident involving Aguero after the City striker disputed a decision with official Sian Massey-Ellis in Saturday's match against Arsenal.
Aguero was pictured placing his hand on Massey-Ellis' shoulder after the official awarded Arsenal a throw-in during the first half of City's 1-0 win at the Etihad Stadium.
The incident was shared widely on social media, with Aguero's conduct under scrutiny, but Guardiola defended the actions of the 32-year-old.
"Come on guys," Guardiola said after the match. "Sergio is the nicest person I ever met in my life. Look for problems in other situations not in this one."
Sky Sports pundit Micah Richard said Aguero "should know better", with the former City defender also praising Massey-Ellis' handling of the situation after the official raised her hand in reaction to the touch before motioning for the striker to walk away.
"I just think he didn't mean to do it really," Richards said. "You've got to respect the officials. I think she deals with the situation really well. He'll know better than that.
"I don't think we need to go over the top on it. He knows not to be touching the officials, it doesn't look good.
"It's just not a good look. We don't need to do that, you start going down a road you don't want to go down - he should know better than that."
Labour MP Dr Rosena Allin-Khan was critical of Aguero's actions when referencing the incident on Twitter.
She said: "Who does Aguero think he is? Completely unacceptable."
Aguero was playing his first match for City since June after recovering from a serious knee injury.
The Argentinian was one of four changes to Guardiola's starting line-up as Raheem Sterling's first-half goal was enough hand City all three points against Arsenal.