Spain under-21 midfielder, David Silva, stunned the home fans in the first half with an absolute screamer, but Ivorian hit man Didier Drogba equalized for the English champions eight minutes after the interval.
Silva received a throw-in from the left flank at the half-hour mark as he moved forward into the Chelsea half before unleashing an unstoppable thunderbolt from 30 yards out into the top corner of Petr Cech's goal.
Chelsea's top scorer Drogba capitalized on Roberto Ayala's misjudgment on Ashley Cole's through ball to catch Santiago Canizares with a clever lobbing header in the 53rd minute.
The game marked the return of Chelsea midfielder Joe Cole who was introduced in the 75th minute following his long-term injury which kept him out for most of the Blues season.
Quique Flores' team managed to resist Chelsea's pressure in search for a winner to end the tie as favorites for the semi-final place after the impressive score line.
The second leg will be played on April 10th at the Mestalla Stadium in Valencia who have a clear advantage of advancing to the semis.