Lionel Messi has been included in the Barcelona squad to face Paris Saint-Germain but he faces a wait to find out if he will start at Camp Nou. A final decision is not expected until Wednesday morning following the hamstring injury he picked up in last week's first leg.

Meanwhile, David Beckham was given hope that, in the absence of Blaise Matuidi, he will be included. The PSG manager, Carlo Ancelotti, defended the former England captain despite criticism after the first leg, insisting: "He has a good chance of playing."

Their Swedish striker Zlatan Ibrahimovic told CNN: "I think he has been very important for us. In the situation that we are in now, the club has been changing from a normal club to a top club, and Beckham gives you some kind of confidence. He has the responsibility, on the pitch and off the pitch, to lead the way for these two months, which is very important. He has a quality, a big quality; he has a touch that I haven't seen many players have. And he is very elegant when he plays."

Barcelona's coach, Tito Vilanova, is again expected to be in the dugout as he was last Tuesday, having returned from two months of cancer treatment in the United States. However, it was his assistant, Jordi Roura, who faced the media on the eve of this quarter-final second leg and by the time the press conference ended Roura could have been forgiven for having lost patience. The first question was about Messi and so was the last. In between, he was mostly asked about Messi. Just as Andrés Iniesta, Maxwell and Ancelotti were. Iniesta admitted that Barcelona are "Messi-dependent."

Even in his absence, the Argentinian was present. The good news was that he was subsequently present in Barcelona's squad but with a 2-2 draw from the first leg he could begin on the bench, to be called upon if needed. When the official list was released, Messi's name, like that of Adriano and Pedro, was followed by an asterisk, denoting a player who had not yet been given the all-clear by medical staff.

His likely replacement in the false No9 role is Cesc Fábregas, who played there against Mallorca on Saturday and scored the first hat-trick of his career. When Roura was asked about Messi for the last time, he replied: "I imagine he is preparing to go out there now. They'll be looking at him, seeing how he is."

Minutes later, Messi strolled into the sunlight at Sant Joan Despí along with the rest of his team-mates and took part in a training session with them – at least for the quarter of an hour that was open to the media.

Messi was taken off at half-time in Paris. He had taken a shot from the edge of the area and then reached for his hamstring. Tests ruled out a tear, a formal statement citing only a "muscle injury" and making no mention of the second leg. "I'll be back soon. Luckily, it wasn't serious," he wrote on his Facebook page.

Only eight days later, it may yet be too soon. "We'll wait a bit," Roura said. "The sensations are good but in the end we'll have to wait until after the session, to see how he is, to see what's happening, and then we'll make a decision. If players play it is because there are guarantees [that they will be fine] but we'll wait to see his progress. We still have today's session and tomorrow's. When the best player in the world is not there of course it is a handicap but, that said, there are lots of players who have played very well lots of times."

Messi has scored 43 league goals this season with Barcelona's next highest, Fábregas, on nine. He also has eight assists, a figure that only three players in Spain can better.

Ancelotti insisted that PSG's approach will not be determined by Messi's availability, which is probably more than can be said for Barcelona. "Without doubt there is Messi-dependence in the sense that he is fundamental for us," said Iniesta. "But there is not Messi-dependence in the sense that this is a team game and we have very good players who can perform well. Cesc is a complete player who understands the game: he combines well with others, he interprets the play and he moves intelligently. He was away for a long time [at Arsenal]. We're lucky that he is back here now."

"But," Iniesta added, "of course Messi is fundamental, irreplaceable, because of what he represents and what he does. He is the No1 when he plays. But if you can't play, you can't play. If he does, it is because they are sure and I am convinced that whatever decision they take will be the right one. It will be an intense match, the pace will be incredibly high and it will be demanding. I hope Leo can play and the same goes for Adriano and Pedro. It will depend on what the doctors think, what Messi thinks and what the coaches think."

There was criticism for Beckham after the first leg, in which he started and played 69 minutes, with L'Equipe giving him a match rating of only three out of 10. But Ancelotti urged him not to take any notice. "Some people criticised David, some people were happy with him," he said. "I was happy, so Beckham has to be happy. I don't know if he will play tomorrow. When the manager is happy [with a player] he has a lot of chances to play."