Second-half goals from Santi Cazorla and Matias Fernandez gave Villarreal a deserved 2-0 win at home to Athletic Bilbao.
Following a tight first half, Villarreal stepped up the pace after the break and took the lead through Spain winger Cazorla with just over 20 minutes left.
The home side missed several good chances to seal it in the latter stages against an Athletic side reduced to 10 men following the dismissal of midfielder Mikael Susaeta.
But Fernandez finally struck the clincher in added time to round off an important victory which keeps Villarreal in fourth place.
Manuel Pellegrini's side finished second last term but have little hope of catching Barcelona or Real Madrid this season.
Finishing fourth and qualifying for the Champions League will be deemed a success for the 'Yellow Submarine', who face Arsenal in the quarter-finals of this season's competition.
The two sides met in the semi-finals in 2006, the Gunners winning before losing to Barcelona in the final.
Villarreal first had to concentrate on the Primera Liga however, and with Atletico Madrid and Malaga just two points behind them at the start of the day, a win was crucial.
But Athletic - who have been somewhat distracted themselves in recent times following their excellent run in the Copa del Rey, in which they will meet Barcelona in the final - proved difficult to break down in an even first half.
Nihat Kahveci tested Gorka Iraizoz with a low shot early on and Igor Gabilondo then tried his luck from long distance at the other end but Diego Lopez gathered comfortably.
Neither side really looked likely to break the deadlock in the first 45 minutes, but Villarreal improved drastically after the break.
Gabilondo almost flicked the ball into his own net a minute after the restart as Villarreal pressured.
And Giuseppe blasted over the bar with only Iraizoz to beat seven minutes later.
Nihat then fired into the side netting as the hosts continued to dominate and it was no surprise when they finally took the lead after 68 minutes.
Rossi took the ball forward and set up Cazorla, who beat Iraizoz with a rasping effort from just inside the box.
Rossi and Joseba Llorente both missed good chances to add a second goal but there was no way back for Athletic, especially after Susaeta received his marching orders following a second yellow card.
Rossi missed another good chance to seal it with five minutes left, but Fernandez popped up to score the second in added time.
The Chile forward left two Athletic defenders in his wake, side-stepped another and clinically slotted past an exposed Iraizoz to wrap up a deserved victory for the home side.
Athletic are now in the bottom half, having lost to the top four sides - Barcelona, Real Madrid, Sevilla and Villarreal - in their last four league games.
Villarreal will stay in fourth whatever happens in Sunday's games.
