The result, along with Barcelona's victory over Real Valladolid, saw Real's lead at the top of the table cut to four points. Valencia struck through David Villa, David Silva and Javier Arizmendi, while Real two goals came from skipper Raul.
Afterwards, Schuster admitted: "What happened today is very hard to take. We played well enough to win and yet finished the game with nothing. But we must accept it and move on.
"In the second-half we paid dearly for our errors. For their winner (Arizmendi's strike) we paid for trying to score ourselves. We left ourselves open at the back and were punished for it. In these type of games, sometimes it is better to play for the draw.
"It wasn't necessary to take such risks at that time."
After five defeats since the resumption of the Liga, Schuster also insisted: "Yes, we've lost many games. But that's because we have paid for our attacking ways. Many of these games we could easily have finished drawing."
"I saw that he was not at the level needed. Admittedly, precisely, he did his best move today before the change, but generally it was not the Robinho we know. We needed something different and Robben gave us another option."
Real sports chief Pedja Mijatovic backed Schuster's summation.
"We had many opportunities and we deserved to win. The ball did not want to enter the goal. At this point, if you are not able to win it is necessary to draw at least, since the points are decisive. There is an advantage of four points and we continue depending on ourselves."