Daniel Sturridge headed in the equaliser as Chelsea drew 1-1 with Birmingham City on Saturday to force a replay of their FA Cup fifth-round encounter after a performance that did nothing to alleviate the pressure on manager Andre Villas-Boas.
The well-organised Championship (second division) visitors had taken a 20th-minute lead through Danny Murphy before their top-flight opponents pulled one back with Sturridge's goal midway through the second half.
Chelsea had squandered an earlier chance to level straight after Murphy's opener when Juan Mata's penalty was well saved by diving Birmingham keeper Colin Doyle.
Later in the day, Arsenal travel to Sunderland in an all-top-flight encounter, while fellow Premier League clubs Everton, Bolton Wanderers and Norwich City face Championship sides Blackpool, Millwall and Leicester City respectively.
Favourites Tottenham Hotspur travel to League One (third tier) Stevenage on Sunday.