Munir El Haddadi, taking full advantage of the absence of Lionel Messi and Luis Suarez, pushed Barcelona into the lead in the 18th minute Wednesday night, Neymar followed up with a second goal seven minutes later and the Catalans were travelling on easy street in the first leg of their Copa del Rey tie at San Mames.
Then came some last-gasp drama.
Athletic Bilbao got a gift goal in the 89th minute from Artiz Aduriz that produced a final 2-1 scoreline and tossed them a lifeline that never looked likely. The second leg will be played next week in the Camp Nou where Barcelona will be favored to advance but they really should not even have had a worry the way they controlled much of the evening.
"It was a difficult game, of course. We lacked fluency in the second half," Barca boss Luis Enrique said after the match. "Regardless of the goal we conceded, I did not think the tie was secure. We go home happy, but [the second leg] next Wednesday will be interesting."
Barcelona was without Messi as a precaution as he nurses a slight hamstring tug and the suspended Suarez, so the front line included the youngster Munir. When he was set up perfectly he made no mistake and he might have had at least one more had he been a bit more patient when sent in clean at the start of the second half. Instead his attempt to chip the goalkeeper from about 40 yards was easily held.
Munir's 18th-minute goal, however, was simplicity itself coming from a very alert piece of football from Arda Turan in his own half of the field. Arda, spotting Athletic's high line, found Ivan Rakitic running behind the defense down the right wing and slipped him a perfect pass; Rakitic carried on in wide open territory, then cut slightly inside before placing his cross on the sliding Munir's boot some eight yards out.
Neymar's 25th-minute finish was even easier as he was alone to strike the ball into an empty net after the Athletic defense collapsed. Iniesta sent the cross in from the left, Sergi Roberto accepted and burst forward down the inside left channel before looking for Neymar up top. Keeper Iago Herrerin advanced to the top of the box to smother the danger, but when he made contact he hit Neymar's legs with his clearance attempt. The Brazilian collected the rebound, stepped between defenders and said thank you very much.
Staked to that lead Barcelona did not need to turn up the pace or intensity the rest of the way, happy with what they had built so easily.
But the Catalans defense went to sleep in the 89th minute, Dani Alves with a dreadful clearance attempt that allowed Aduriz to give Athletic their unexpected goal. The ineffective clearance went straight to Mikel San Jose who found Arduriz alone left. Aduriz calmly beat Marc-Andre Ter Stegen and made the scoreline flatter Athletic but it also meant the tie remained alive.
Earlier in the night, Celta Vigo and Atletico Madrid shared a 0-0 draw in the first leg of their Copa del Rey quarterfinal in Vigo, neither team producing enough of an attacking spark to the break the deadlock.
As a result, the second leg next week in Vicente Calderon will determine who advances to the semifinal round. Celta will probably be pleased with not conceding an away goal, but Atletico will fancy its chances in front of the home fans.
"Any tie now will benefit them and that is what stands out for the next match," Atletico boss Diego Simeone said after the draw. "From the moment that we advanced to the last qualifying round, we knew that more and more effort and more work would be required as a result of the responsibility you have in the competitions and the demands of the matches."
Simeone continued his pattern of giving back-up keeper Miguel Angel Moya a Cup start and also gave games to Jesus Gamez and Stefan Savic in the back foul, Juanfran and Jose Maria Gimenez unused off the bench. Fernando Torres, continuing to nurse an ankle injury picked up in training a week ago, was again missing from the 18.
Celta had the better of a scoreless first half, John Guidetti and Pablo Hernandez looking the most dangerous, but Atletico's defense was its usual tight self and Moya never had to be anything more than efficient. Atletico got little going the other way, Jackson Martinez again failing to make an impression at the head of the attack and Antoine Griezmann seeing nothing of the ball.
There was considerably more enterprise from Atletico as the second half began, but no breakthrough so Simeone sent Angel Correa on for Martinez at the hour mark. Six minutes later Luciano Vietto replaced Carrasco as Atletico still searched for the right combination to no effect.
Celta was not getting the possession it had enjoyed earlier, having to chase much more, but as the clock ticked on the home side seemed content to hold onto what they had and leave things to be decided next week. They nearly got a gift in the 82nd minute when miscommunication in the back saw Augusto Fernandez touch a ball past the advancing Moya as Guidetti chased, but there was just enough time for Gabi to get back and sweep it off his own line.
That was as close anyone came although Celta had a loud penalty shout turned down in the 90th minute when header to a corner appeared to strike a defender's arm.
Information from Goal.com was used in this report.