"I felt it as soon as he came onto the field and his first touches of the ball," said Pochettino in quotes reported by L'Equipe.

"He brought a calmness to the team. It's very important to get off to a good start, even for him.

"He was happy and he is well integrated into the group. It was a question of common sense to give him his debut."

The six-time Ballon d'Or winner signed a two-year deal in the French capital on August 10 after ending a 21-year spell at Barca, but he had not played since winning the Copa America with Argentina on July 11.

"The welcome, it was something beautiful to see and hear from our supporters, but also from Reims fans. Messi was very happy about it," added Pochettino.

"The motivation of the competition is there for everyone, but his presence brings optimism.

"Everyone feels it. It has an influence on the other players."

Mbappe opened the scoring after 15 minutes when he got between two Reims defenders to head the ball into the back of the net from a well-weighted Angel Di Maria cross.

With Reims having seen a goal chalked off by VAR, Mbappe added his second three minutes past the hour mark.

Achraf Hakimi broke forward before sending an inch-perfect pass into the path of the French forward, who tapped it home to double his side's lead.

Messi had to wait 10 minutes after coming on for anything resembling a goalscoring opportunity. The 34-year-old drove forward before passing to Mbappe, but the return pass could not find the Argentinian.