Spain had to wait until the final 23 minutes before a trio of strikes against ten-man Croatia took them through to next summer's UEFA European Under-21 Championship finals.
The visitors' 2-1 victory on home soil in Saturday's opening leg had left this tie in the balance, but Croatia were hit by an early injury to captain Ivan Rakitić and received a further setback when Álvaro Domínguez registered on 67 minutes. Dejan Lovren's dismissal shortly afterwards made their mission even tougher and Spain confirmed their place in Denmark courtesy of late goals from Adrián and Jeffren.
Croatia's chances began to unravel as soon as FC Schalke 04 winger Rakitić had to leave the pitch after just 14 minutes with a head injury. Mirko Oremuš came on in his place, but Spain began to dominate after that and created three excellent chances in the first half, only to fail to put them away. They needed to be patient before making their breakthrough, yet it came eventually when Ivan Kelava failed to claim a Juan Mata corner, allowing Domínguez to pounce.
Lovren collected the first of his yellow cards almost immediately after that goal and three minutes later he incurred a second, giving the visitors a numerical advantage that they exploited when Adrián added to his effort in the first leg by profiting from another lapse at the back by Croatia. In the first minute of added time, substitute Jeffren put the cap on Spain's joy at the end of a counterattacking move.
"It was a tough match because Croatia have fast, quality players," said victorious coach Luis Milla. "Our first goal was to get into the European Championship and we'll be going for a spot in the Olympics now." His opposite number Dražen Ladić lamented missed opportunities, meanwhile. "We weren't playing at our best today and couldn't win with our talent alone," he said. "Against Spain you mustn't waste your chances and we did exactly that."