Still nothing can separate these teams but in eight days' time something must. Atlético Madrid and Barcelona met for the fourth time this season and for the fourth time they drew. Neymar equalised Diego's astonishing opener, which had ripped through the air and into the net. It finished level and both managers declared themselves satisfied, but that away goal may prove to be a precious advantage for a team with the Champions League's best defensive record.

It had appeared to be a disaster when Diego came on. Not because it was he who entered the pitch but because of who it was leaving it, hobbling slowly, sadly, in the other direction, seeming to take much of Atlético's hopes with him. Diego Costa lasted just 29 minutes, pulling up with a hamstring injury. He was the second to depart: Gerard Piqué fell heavily 12 minutes in; a hairline fracture of the pelvis will keep him out for four weeks.

Costa had seven goals in five Champions League games and Atlético were already without the suspended Raúl García. David Villa was still there, though, and the best first-half opportunities came his way; after four minutes he swung a shot wide and after 44 minutes José Pinto palmed away his bending effort.

Between those there was a familiar, if broken, pattern. Atlético's early push faded. The ball was largely Barcelona's but there remained a vulnerability about them and creating openings was difficult. In the three previous meetings there'd been just two goals. Barcelona had an average of 72% possession but a total of only seven efforts on target. In the opening 45 minutes here there were headers from Neymar and Lionel Messi, both comfortably saved. Then Messi escaped Miranda with wonderful footwork and delivered a sharp pass into Andrés Iniesta to hit hard and low. Diego Godín flew across to make a superb block.

Diego Simeone had said that Barcelona's game is built around the ball while Atletico's is built around the space and that was an accurate portrait. Barcelona's passing lacked the swift precision needed. Cesc Fábregas lacked influence and the longer it went the more surprising the absence of Pedro or Alexis Sánchez was. When Atlético attacked, space opened before them. The danger was clear. What no one imagined was that the goal would come like it did. Diego received the ball 10 yards outside the right-hand corner of the penalty area. He turned, stepped away from Xavi and thumped a swerving rocket into the top corner by Pinto's near post.

"I'm very proud of the team: they're a team of enormous heart," the Atlético manager, Diego Simeone, said. Barcelona's coach Gerardo Martino too said he was "proud" of his side. Playing like this, he insisted, there is hope in the second leg.

Iniesta went down but was waved up, Sergio Busquets brought a save from Thibaut Courtois and Dani Alves's thumped cross hit Messi's midriff. Alexis replaced Fábregas and there was more to the attacks. With 20 minutes left Iniesta played an impeccable pass with the outside of a foot through a passageway of defenders, Neymar opened up his body and side-footed into the corner.

Iniesta had carried the greatest threat and incision. Courtois dived to push Iniesta's shot wide and then tipped away Messi's curling free-kick. As the clock ticked, Barcelona pressed, and by the end they had taken 17 shots but the second goal resisted. A fourth meeting yielded no winner. Next week, they meet again.