But the result came at some cost for Frank Lampard – he saw star striker Tammy Abraham leave the field on a stretcher at the end of the first half.
The England striker suffered a heavy fall just minutes before the interval and was in clear pain as he was helped to the sideline.
Mateo Kovacic put the visitors to the Mestalla 1-0 up with his first goal for 141 games, but Carlos Soler equalised with a scrappy effort.
Christian Pulisic then put Chelsea 2-1 up as he poked home Kurt Zouma’s knockdown – but that took five minutes to be given after VAR checked it out
Just as it seemed Lampard’s troops would get three points that would all-but guarantee progression out of Group H, Daniel Wass curled in a fluke that left Kepa stranded.
It was harsh on the Chelsea stopper, who had earlier saved a Dani Parejo penalty with a stunning effort – with the dreaded VAR again causing no ends of delay.
Rodrigo’s glaring miss at the death could even have sealed Valencia’s place in the last 16, but a compelling, gritty game somehow ended even.