Leo Messi may have only played 30 minutes and he looked to still be carrying a hamstring strain, but his entry on the pitch was still enough to help Barca into the last four of the Champions League.

Barca were a goal down and suffering as they have not suffered for a long time in Europe, before Messi came on and even though his contribution was almost testimonial, he did enough to raise his side and set up the vital equalizing goal which was enough to decide a nerve wracking quarter-final second leg.

As expected Messi had begun the game on the subs' bench for Barca after failing to recover fully from the hamstring injury he suffered in Paris a week previously.

There was a surprise in the Barca defense, however, as Adriano Coreira was preferred to Marc Bartra although he is not a specialist central defender. Meanwhile Paris had three former Barca players: Zalatan Ibrahimovich, Maxwell and Thiago Motta, in their starting 11, although David Beckham was also on the bench for the French side.

The game kicked off with Barca having their chance to take the lead in the game and also the tie as Xavi Hernandez hit a free kick inches wide of the Paris post, in the second minute.

But that was virtually as good as it got for the home side in the first 45 minutes as Paris arrived in the Barca area with ease and the home side had goalkeeper, Victor Valdes to thank for keeping the score at 0-0 as the keeper made several excellent saves to deny Ezequiel Lavazzi, who robbed Sergio Busquets in midfield, Lucas Moura, Lavazzi again, who drilled in a low shot after 25 minutes, and Moura for a second time after a powerful far post header.

Barca were struggling in midfield, with Busquets looking lost, while Xavi appeared to be still off the pace as a result of his recent hamstring problems as Barca put in one of their worst first 45 minutes in Europe for a long time.

Paris had deserved a goal and they got it after Javier Pastore sprang the offside trap to beat Valdes, who got a touch on his shot, but was unable to keep the ball out just five minutes after the break.

That was the sign for Messi to start warming up, as Barca continued to look lost, but it was not until Dani Alves had fired over the bar just after the hour that Messi got into the game, along with Bartra who replaced Adriano, while Cesc left the pitch for Messi.

The Argentinian's entry into the game produced a moral effect for his side and they almost leveled after a scramble as Iniesta' s shot was blocked and Messi's control for once let him down.

With 20 minutes left, it looked as if the 'Messi effect' had worn out, but then the Barca number 10 collected the ball, fed David Villa and Villa's layoff teed up Pedro to rifle home the equalizer.

The game was not for those of a nervous disposition, especially as Messi looked to still be struggling with his injury and although Iniesta produced a moment of magic in the closing minutes his shot went wide.

The game ended with Barca doing what they never do: hit long clearances and praying for the clock to tick down, but tick down is what it did and though they were way below their best, Barca are in the semi-finals for the sixth consecutive season.