Spain coach Vicente del Bosque admitted the defending champions were not at their best despite beating Croatia 1-0 in Gdansk to reach the quarter-finals of Euro 2012 on Monday as Group C winners.

"The team played well, even though things didn't go according to plan," said Del Bosque, who started but then took off Fernando Torres for Jesus Navas of Seville, who promptly bundled in the only goal of a somewhat shapeless match which could have gone either way.

The World Cup winners topped the group with seven points after their opening draw with Italy and 4-0 rout of Ireland, Slaven Bilic's Croatia bowed out with four points after Italy leapfrogged the Croats with a 2-0 win over Ireland.

"There was a lack of clarity compared with other occasions," said Del Bosque.

"The truth is it was not a great game overall and this should concern us," said the moustachioed Del Bosque, who took over after Luis Aragones had led the Furia Roja to glory in 2008 before he himself masterminded further success at the World Cup in South Africa.

Another European title this summer will make history as no country has won three major events on a roll before.

"We were fighting for a victory, not a draw, and we have taken a step forward here by qualifying, this is motivation for the quarter-finals," Del Bosque told reporters.

"We did not have many clearcut chances, which is also to their credit," said Del Bosque, whose men now likely face either France or England from Group D after surviving a test of patience and nerves given that a Croatian win coupled with Italy's success would have left them eliminated.

"We have no preference whether it is France, England or Ukraine, we have to be ready to take whatever comes," said Del Bosque of the next hurdle.

Asked if he could put his finger on what had been lacking in Monday's showing he said: "Our first touch was not so good and thanks to that we dipped in terms of speed and intensity.

"We suffered but then so did they. We had 17 efforts on goal to eight for them and also more possession than them.

"But Croatia played well - they did not let us play in our comfort zone, closed down the spaces and tried to hit us on the counter-attack, though we were mostly in control."