Mauricio Pochettino said that Lionel Messi is still "far away" from his best form after handing Messi his Paris Saint-Germain debut during their win over Stade de Reims.
Two goals from Kylian Mbappe powered PSG to a 2-0 victory but it was the arrival of Messi in the 66th minute that supporters of both clubs greeted with a standing ovation.
The Argentine joined the club from Barcelona this summer and the fixture against Reims marked the first time Messi has played club football for anyone other than the Catalan side.
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His new manager Pochettino praised the "optimism" and "calmness" that Messi added, but warned that he is not yet back in full flow after a busy, dramatic summer.
"We are waiting for the best from him," Pochettino told Amazon Prime after his side's victory.
"He is still far away from his best form but he has been training well and he will be fit in the next two weeks.
"I'm very happy he made his debut. It was good to hear the crowd cheering him, not just our supporters - it is something Leo has earned."
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Mbappe is the subject of continued links with a move to Real Madrid after the arrival of Messi in Paris.
It has been an explosive summer of transfer activity for some of Europe's biggest players and clubs, and Real Madrid are reported to be waiting for a response to their bid for the player, believed to be a figure in excess of 160 million euros.
"Kylian is our player and you know that in football there is always gossip and rumours," said Pochettino of Mbappe's future.
"He is one of the best, one of the most important players in the world today and for him to be with us is a gift."
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Messi has been named in the Argentina squad due to play fixtures against Venezuela, Brazil and Bolivia in the next two weeks, along with club-mates Angel Di Maria and Leandro Paredes.
Of his new marquee forward's cameo, compatriot Pochettino added: "Every time he touched the ball he spread calm through the team.
"He is Messi: he can radiate an optimism and energy that everyone can feel and that have a positive influence on our players.
"It's important even for Lionel Messi to win on his debut."
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