"With Barcelona you have to defend, but when you have the ball you need to be dangerous and have good attacking ideas ... I have confidence we can do it."
The team's two superstar strikers cancelled each other out in a frenzied atmosphere at Parc des Princes, with Messi putting Barcelona ahead with his 57th goal of the season before his injury. Zlatan Ibrahimovic replied for PSG before setting up Matuidi's last-gasp equaliser in the final seconds.
The Catalans will be annoyed at not going home with a lead, however, after Xavi Hernandez's 89th-minute penalty looked certain to seal victory, but goalkeeper Victor Valdes allowed Matuidi's deflected strike to squirm under his body and over the line.
Barca, who remain the firm favourites, will also be missing midfielder Javier Mascherano for the return after he went off on a stretcher near the end with ruptured knee ligaments. He faces six weeks out.
PSG will be without Matuidi for the return leg because he is suspended.
"It's a blow for us because Blaise is an important player," Ancelotti said.
But Messi's possible absence would give PSG greater reason to hope, especially with Ibrahimovic likely to face a depleted defence.
"It's going to be tough there but it's not going to be impossible," PSG midfielder David Beckham said. "Ibra can cause any team problems when the ball is played up to him, he is so strong and physical."
Messi, who was replaced by Cesc Fabregas for the second half, is having more tests to check out his injury.
Both coaches felt aggrieved at refereeing decisions, with Jordi Roura complaining that Ibrahimovic's goal was offside and Ancelotti saying Alexis Sanchez dived to win the penalty.
- AP