Chelsea were the first to seriously threaten when a cross from Graeme Le Saux picked out Hasselbaink at the near post only for the 24-goal front man to head wide.
Chelsea looked more purposeful in the early stages but the home side started to come more into the game and Merson curled a 25-yard shot just off target.
Then after 28 minutes it was Merson who broke the deadlock with his third goal of the season.
Boateng sent in Vassell and he burst into the box only for his shot to ricochet off Desailly and Merson was on hand to stick out his leg and divert the ball past Carlo Cudicini into the corner of the net.
Gudjohnsen then wasted Chelsea's best chance of the opening half when Desailly squared the ball back into his path and, from barely six yards out, he lofted his shot over the crossbar.
Blues boss Claudio Ranieri made a double substitution, sending on Gianfranco Zola and Mikael Forssell and switching to a 3-5-2 system - and within a minute Chelsea were back on level terms.
Zola's floated pass caught Villa napping and Hasselbaink nodded the ball down into the path of Frank Lampard who drilled a low shot past Enckelmanin the Villa goal.
Chelsea pressed hard for the winner and Forssell was only inches too high with a curling effort and Enckelman was fortunate that a deflected Hasselbaink free-kick flew straight into his arms.
In the dying minues Hasselbaink raced clear of the Villa defence but screwed his shot past the far post while Enckelman made a fine block to keep out a last-ditch effort from Stanic.
And so Chelsea had to settle for a point although their performance deserved all three!
Review the information and discuss it on the messageboard.