Chelsea were forced to settle for a point against Blackburn after a second half "goal" was controversially ruled out by referee Howard Webb.
Chelsea looked to have sealed all three points when Salomon Kalou converted a cross from Julian Belletti but Webb disallowed the goal for offside.
Chelsea had squandered a host of first-half chances but Blackburn could have stolen the points themselves if Petr Cech had not tipped Robbie Savage's late effort over the crossbar.
But Blackburn's point was overshadowed by a serious head injury to defender Christopher Samba.
The opening 15 minutes failed to produce clear-cut opening although Blackburn 'keeper Brad Friedel was called on to hold a tame header from Chelsea skipper John Terry.
Blackburn, one of the teams identified by Chelsea coach Jose Mourinho, as adding strength to the Barclays Premier League, proved they were worthy of his praise with some clever attacking play.
However, Rovers were thwarted on numerous occasions by the last-ditch efforts of Terry and Ashley Cole as the goalscoring threat from Benni McCarthy and Roque Santa Cruz threatened to puncture the home defence.
Chelsea were bidding to take their unbeaten home run in the top flight to 66 games but without the driving force of the injured Frank Lampard in midfield and the strength of Didier Drogba in attack, the Blues struggled to gain control of the game.
Later on, Belletti's cross was turned in by Kalou but was controversially ruled out by referee Howard Webb for offside.
The decision sparked uproar on the bench with Mourinho and assistant Steve Clarke berating the fourth official Peter Walton and remonstrating with him to look at the touchline TV screen.
It ended with Webb having to ask Mourinho to calm down but TV replays suggested the Chelsea manager had a good case for the goal looked to be perfectly legal.