Dusan Svento's early goal was enough for Salzburg to win 1-0 at Villarreal and finish the Europa League group stage as the only team with a 100% record.
Slovakian Svento scored the game's only goal in the seventh minute as Huub Stevens' team bagged all 18 points in Group G.
Just like Salzburg, Villarreal also were already qualified for the last 32 going into the game. The Primera Division side finished second in the pool on nine points.
The Austrian outfit, who conceded just two goals in their six group victories, showed their attacking intend from the outset in Spain and took the lead after just seven minutes.
Simon Cziommer sent a long ball over the Villarreal back-line for Svento, whose left-footed shot beat Xabi Oliva at his far post.
Stevens' team controlled the hosts for much of the next 20 minutes. The Spanish side did muster a good chance on the half-hour mark, but Joseba Llorente could not lift the ball over the charging Salzburg goalkeeper Eddie Gustafsson.
The home team got the better of Gustafsson six minutes later but Cziommer cleared a dangerous ball into the area from Jonathan Pereira.
The visitors had an opportunity to go two up two minutes after the break but Robin Nelisse's shot did not have the pace to beat Oliva.
Ernesto Valverde's team continued to push forward looking for the equaliser and nearly found it in the 61st minute. Damian Escudero's corner from the right was misjudged by Gustafsson, but the goalkeeper was rescued by the crossbar.
The Yellow Submarine appeared determined to inflict a first loss on the Austrian side, but Salzburg stood firm defensively over the final half-hour.
Giuseppe Rossi found himself well positioned with 11 minutes left but shot well wide from 12 yards, much to the visitors' relief.
Salzburg, however, almost made it 2-0 on the counter-attack in stoppage time. Admir Vladavic struck narrowly off target but the away team had done enough.
