The west Londoners failed to hit their usual impeccable standards at the St Mary's Stadium on Sunday, with Southampton displaying their top-four credentials in a battling display.
An upset appeared on the cards when Sadio Mane made the most of sloppy defending from Chelsea captain John Terry, recently promised a new deal by Mourinho, to race through and deftly lift over Thibaut Courtois for his second goal in as many matches.
But Mourinho's side had to settle for a point - despite an 88th-minute red card for Southampton's Morgan Schneiderlin.
His expertly dinked throughball caught Terry flat-footed and the Chelsea skipper was left trailing in Mane's wake as the Senegal winger sprung the offside trap and kept his cool to lift the ball over Courtois.
Fabregas was again involved 10 minutes after the break when he was tripped inside the penalty area by teenage full-back Targett – making his first league start in place of Chelsea loanee Ryan Bertrand – but referee Anthony Taylor deemed it a dive and booked the incredulous Spaniard.
The visitors continued to press and Fabregas once again teed up Hazard on the hour but this time he flashed wide of the right-hand post, while Didier Drogba was introduced to add muscle to Chelsea's attack.
However, for all the visitors' pressure a clear-cut opportunity never materialised and even when Schneiderlin received a second yellow card and subsequent red for hacking down Fabregras on the half-way line Chelsea could not find a way through, missing the chance to keep daylight between themselves and Manchester City.
