Swansea's Group A trip to the Mestalla was, on paper, the standout of all those played in the Europa League on Thursday, but few could have imagined it would be so one-sided.
A Swansea side coached by former Real Madrid and Barcelona star Michael Laudrup and featuring six Spaniards, including captain Angel Rangel, punished opponents who played 80 minutes with ten men to run out thoroughly deserving winners.
Valencia were already wobbling before French centre-back Adil Rami was sent off with ten minutes on the clock for hauling back Wilfried Bony as the Ivorian striker headed towards goal.
Soon after, the lively Bony converted a Michu cutback to give Swansea the lead, and Valencia, who have lost their last three matches in La Liga, never looked like recovering.
A section of the Valencia support staged a walkout in protest at their teams' recent form at the start of the second half, before Spanish duo Alejandro Pozuelo and Michu combined for the latter to double Swansea's lead after 58 minutes.
When Jonathan De Guzman beat Vicente Guaita with a stunning free-kick five minutes later, the home supporters could only applaud, and Swansea might even have won by a greater margin.
It was a stunning victory for a club that lost 8-0 to Monaco in their last European tie in the Cup Winners Cup in 1991.
"It was a fantastic game," Laudrup said afterwards. "Of course the red card was an influence -- but we dominated from the first minute to the last.
"It could have been more than three and I'm very pleased to beat a club like Valencia. It was our fifth game in Europe -- and we were facing a big team."
The win was only the second by a Welsh side against Spanish opponents in European competition, after Cardiff City beat Real Madrid 1-0 in the Cup Winners Cup quarter-final, first leg, in March 1971. Cardiff lost 2-0 in the return.
Defore grabs brace
Meanwhile, Tottenham also won by a 3-0 margin, although their victory against Norwegian top-flight strugglers Tromso in Group K was a little less dramatic.
A first-half brace by Jermain Defoe, which took him to within two goals of Spurs' all-time leading European goalscorer Martin Chivers, effectively ended the contest inside half an hour.
However, Danish midfielder Christian Eriksen, a recent signing from Ajax, added a superb third goal late on.
"It was the perfect start," Spurs manager Andre Villas-Boas said. "It was important to score three points straight away."
Villas-Boas hopes the injuries picked up by Younes Kaboul, Danny Rose and Moussa Dembele will not prove to be serious.
"We had some good moments. It was a difficult game because of the injuries we suffered but I am very pleased with the performance."
Elsewhere, English FA Cup holders Wigan Athletic took time out from their bid to win promotion back to the English Premier League to draw 0-0 away to Zulte Waregem in Belgium in Group D.
However, the 1988 European Cup winners PSV Eindhoven suffered a shock 2-0 defeat at home to Ludogorets Razgrad of Bulgaria in Group B, and an expensively assembled Dynamo Kiev side lost 1-0 at home to Belgian Cup holders Genk.
Jonathan Soriano produced one of the individual performances of the evening, scoring a hat-trick in Europe for the second time this season as Salzburg beat Elfsborg 4-0 in Group C.