Victory in the final against Dutch side, Heerenveen, meant Villarreal would debut in the 2003-2004 UEFA Cup. And a historic participation it was, with the Yellows reaching the semi-final stage of the second most important club tournament in Europe.
The Submarine opened its campaign against Turkish side, Trabzonspor. But Villarreal was unable to cheer the crowd with an opening victory, the match finishing 0-0 at El Madrigal with all to play for in the second leg. The Yellows finally won through with 2-3 victory in the Turkish cauldron dispelling any doubts created by the goalless first leg. Anderson and José Mari with a brace were on target for the Yellows.
Villarreal now faced four more rounds before reaching the semi-finals, an amazing achievement for a club making its debut in a major European competition. In the second round Torpedo Moscow was beaten (2-0 and 0-1), Galatasaray went down 2-2 and 3-0 in the third, Roma 2-0 and 1-2 in the fourth, and Glasgow Celtic 1-1 and 2-0 in the quarter-finals in a match that saw both clubs establish a bond of friendship with each other.
In the semi-finals the Yellows were drawn against Valencia CF in a clash between two sides from the Valencian community. A match won by the ‘Ché’ faction thanks to a goal by Mista from the penalty spot in the second leg, the only goal after 180 minutes of football, but enough to punish the Yellows and keep them out of the first European final.