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 remains the firm favorite, will also be missing center half Javier Mascherano for the return after he went off on a stretcher near the end after rupturing knee ligaments. He faces six weeks out.
PSG will be without Matuidi for the return leg as 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 be up against a depleted defense.
"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, will have further tests on Wednesday to determine the extent of his injury.
"We've paid a heavy price, because we've lost Messi, and Mascherano,'' Roura said. ``Of course it will be a big loss if we lose Messi, the best player in the world. But we have Cesc and other options, so we are confident from that point of view.''
Both coaches felt aggrieved at refereeing decisions, with Roura complaining that Ibrahimovic's goal was offside and Ancelotti saying Alexis Sanchez dived to win the penalty.
That came after a superb passing move opened up PSG's defense on the left and Sanchez ran through before being tripped by goalkeeper Salvatore Sirigu. With Messi normally taking Barcelona's penalties, Xavi dispatched the spot kick with all the composure of someone who has won two European Championships and a World Cup for Spain.
PSG had the better of the opening half had Messi almost completely contained until Dani Alves set him free in the area with a delicately lobbed pass, and the four-time player of the year clinically dispatched it into the far corner.
Ibrahimovic had wasted a couple of chances before finally getting the equalizer. Thiago Silva's glancing header hit the post, and the Swede stretched out a giant leg to poke the ball into the bottom corner although replays showed he had been offside.
Beckham was handed only his third start for PSG in central midfield alongside Matuidi, the former England captain's vast experience seeing him preferred to the inexperienced 20-year-old Marco Verratti.
"I put Beckham there because he has the ability to play forward passes and change the play,'' Ancelotti said. ``He played really well with good passes, changing sides. That was the reason I put him on the pitch.''
Barcelona coach Tito Vilanova was back in charge for the first time since returning from a 10-week medical stay in New York, where he received treatment after the removal of a throat tumor in December.
PSG came close to scoring in the fifth minute when Javier Pastore chested the ball into the path of winger Ezequiel Lavezzi as he cut inside from the right of the area. Barcelona midfielder Sergio Busquets came across to tackle him and his clearance struck the post.
Ibrahimovic was hauled down after a surging run in the 18th and Valdes made a great save from his subsequent free kick.
Silva managed to contain Messi early on, making an outstanding double tackle to rob him of possession just inside the area. But Messi can never be subdued for long, and he scored his eighth Champions League goal of the campaign with his first chance. It was his 59th in the competition overall, second to all-time leader Raul Gonzalez's 71.
