Nuno’s men could have re-established their two-point lead over fifth-placed Sevilla with victory but they fell behind to Adri Embarba’s first-half goal.
Dani Parejo levelled with a free-kick immediately after Jorge Morcillo had been sent off, but the visitors too finished with 10 men after Rodrigo was dismissed for a petulant kick out at Tono, who could have been given his marching orders for his part in the fracas.
In between the two dismissals, Vallecano manager Paco Jemez was sent to the stands for his remonstrations at several incidents going against his side.
Valencia had the best of the early opportunities, with captain Parejo twice going close before Andre Gomes saw his effort deflected over the bar.
Yet it was Vallecano who took a 19th-minute lead in rather fortuitous circumstances.
Embarba held off several challenges to dribble to the edge of the area but his tame effort looked to be heading into Diego Alves’ hands, only for the Brazilian goalkeeper to clumsily spill the ball into the net.
On-loan Manchester City forward Alvaro Negredo spurned two glorious opportunities to level, both times failing to make proper contact with the ball when wonderfully picked out by Rodrigo.
Los Che continued to pour forwards and an intricate move ended with Pablo Piatti shooting straight at Vallecano custodian Tono.
Parejo was denied by the post after the interval from just outside the area but then the visitors were given a helping hand in the pursuit of an equaliser when Morcillo was given a straight red card for bringing down Gomes, who was through on goal.
While it was a clear foul, Vallecano were furious as Negredo was in an offside position in the build-up and prevented Ze Castro from potentially catching Gomes.
To add salt to the wound, Parejo expertly placed his free-kick into the top corner in the 66th minute to draw Valencia level.
Boos rang around the ground and the game started to grow increasingly unsettled as Vallecano boss Jemez was sent to the stands just a few minutes after the leveller.
Vallecano, in a rare venture forward in the second half, could have retaken the lead but Alves made amends for his earlier error to produce a wonderful acrobatic save from Gael Kakuta’s strike.
It was Los Franjirrojos who were grateful for a slice of fortune in the 78th minute when Rodrigo was giving his marching orders for kicking out at Tono, who had appeared to have landed unnecessarily heavily on the Valencia forward.
Despite the numbers being evened up, it was the visitors who looked the stronger in the closing stages but they could not find another way through.