The absence is a problematic one for PSG, not just because Messi is out against Metz. They have a busy schedule coming up, with Montpellier on September 25, Manchester City on September 28 and Rennes on October 3.
Pochettino discusses Messi's knee injury
In a press conference on Tuesday, Pochettino was asked about the Messi substitution again and about the knee injury.
"The club already released a statement about what he had and I think it's quite clear," the coach stated.
"We saw he was checking his knee on the sidelines with gestures and you could also notice he had an issue when he took a shot.
"He'd had a good first half and we were happy with his performance, but we decided to take him off based on the information we have.
"I understand the media reaction, but our priority is always to look out for the player.
"The best players always want to be on the pitch, so I'm not surprised Messi wanted to continue."
PSG also provided updates on Marco Verratti and Sergio Ramos this Tuesday, with the midfielder and centre-back continuing with their own recovery processes as they aim to make it back on to the pitch soon too.