Messi was back in training Monday after being suspended for making an unauthorised trip to Saudi Arabia and missing a training session as a result.
“I spoke with him on Tuesday to see what his mindset was and I found him very determined to play. … He will start tomorrow,” Galtier said at a news conference.
Messi’s future at PSG has been the subject of much speculation recently, with sources telling ESPN that the Argentina captain will leave the French champions at the end of the campaign. Sources added that he had received a formal offer to join Saudi Arabian club Al Hilal next season.
The player’s focus is on winning the French title, however, Galtier said.
“He’s very eager to win that title,” he added. “With him in the team we’ll have to adjust compared to what we did against Troyes. Leo is Leo. I’m not going to go into statistics but when he’s with us we have to strike a different balance.”
PSG’s season has been well below expectations, having suffered early eliminations in the Champions League and the French Cup.
Lens will move provisionally three points behind PSG if they beat Stade de Reims at home today.
PSG have lost three of their past four home games.