Bojan Krkic scored the only goal of the game in the 12th minute, earning Frank Rijkaard’s side an important away goal on top of the slender lead they take into the second leg.

Schalke were outplayed in the first half before coming to life in the second, but they were unable to find a goal, leaving them with a mountain to climb at the Nou Camp next week.

Schalke coach Mirko Slomka surprised many with his bold team selection which included Gerald Asamoah and Halil Altintop alongside Kevin Kuranyi in a three-man attack.

Barcelona responded with a trident of their own composed of Thierry Henry, Bojan and Samuel Eto’o, who had been passed fit to play on Tuesday morning.

It was the Barca threesome which sparked into life first.

Henry’s shot was fumbled by Manuel Neuer, but the Frenchman squared the rebound to the unmarked Bojan who tapped in from two yards.

It was the perfect conclusion to a move which stemmed from the industrious Andres Iniesta who, along with Xavi, was pulling the strings in the Barca midfield and had already carved out a good chance for himself in the seventh minute when Neuer made a reaction save.

Barca were on top thanks largely to a midfield which moved with fluidity while Schalke’s lacked cohesion and, at times, organisation.

Eto’o was finding a lot of room on the right wing and his dangerous low cross almost forced home defender Marcelo Bordon to turn the ball into his own net only for the ball to flash past the post.

Schalke began to gain more belief as the game progressed and Asamoah claimed a penalty when he was challenged from behind by Eric Abidal as he pulled the ball back for Altintop to drill wide.

Schalke’s belief moved up another level early in the second half when they managed to test Victor Valdes for the first time.

Altintop sent the first warning from the angle of the 18-yard box with a shot which fizzed past the far post, taking a deflection on the way.

After the resulting corner, Schalke regained possession and Christian Pander’s powerful shot from 25 yards was too hot for Valdes to handle, but no Royal Blues player had gambled and Gabriel Milito had plenty of time to clear the loose ball for a throw-in.

Milito had a more complicated clearance to make to deny Kuranyi a free header from Pander’s cross before the Schalke number nine was withdrawn on the hour mark for Vicente Sanchez – a move which was met with a few derisory jeers for Kuranyi.

Barca were unable to regain control of the midfield as Schalke kept up the pressure with Fabian Ernst’s shot only inches away from Asamoah after Pander had waltzed past Gianluca Zambrotta and Xavi in the 70th minute.

Altintop had the next opportunity but appeared to be caught in two minds between shooting and crossing, and did neither with a poor effort which was too strong for Asamoah to convert at the far post.

Substitute Soren Larsen then headed wide from a Heiko Westermann cross before the latter got on the end of a cross himself, although he too was unable to direct it goalwards, instead claiming he had been impeded by Abidal.

Valdes tipped Bordon’s stoppage-time header over the bar as Barca held on to move a step closer to a last-four clash against either Roma or Manchester United.