Valencia missed the chance to take a stranglehold on Group B after they were left with egg on their face after allowing struggling Slavia Prague to battle back from 2-0 down to draw 2-2 despite playing with 10 men for most of the second half.
With Lille heading to defeat in Genoa, in-form Valencia looked set to take over top spot after going ahead in Prague through Joaquin Sanchez's first-half penalty and Hedwiges Maduro's thunderbolt at the start of the second period, before Slavia lost Zdenek Senkerik to a red card in the 49th minute.
However, Slavia made a mockery of their dismal recent record in Europe - they had won just one of their previous 22 victories on the continent - by hitting back to take a share of the spoils thanks to late goals from Petr Janda (79) and Peter Grajciar (82), before Valencia's misery was compounded when they had Ruben Baraja sent off in injury-time.
The result means Valencia remain in second place in the group, one point behind Lille but now level on six points with Genoa. Slavia are still bottom with just two points - both of which have now come against Valencia.
Valencia, who drew 1-1 with Slavia at the Mestalla a fortnight ago, needed just 24 minutes to go ahead when they were awarded a penalty after David Hubacek tripped Juan Manuel Mata inside the area.
With star striker David Villa suspended following his red card in the first meeting with the Czechs, winger Joaquin stepped up to take the penalty and he gave Slavia goalkeeper Deniss Romanovs no chance with an unstoppable shot into the top corner.
The Spaniards then saw a seemingly legal Mata goal soon after ruled out for offside, but they need not have worried as they did make it 2-0 three minutes after half-time when Maduro brought down a clearance 25 yards out before slamming a superb rising shot into the far top corner.
It was all going Valencia's way at that stage, and the dismissal of Senkerik for a second yellow put them in further control before Baraja headed one of a number of chances against the Slavia crossbar.
However, there was to be a late twist as, against the run of play, Slavia scored twice in three minutes to take a point, Janda heading from Grajciar's corner and then Grajciar firing home after Adam Hlousek had seen his effort saved by Miguel Moya.
