Having scored in the first half to give the beleaguered reigning champions the lead at Stamford Bridge, Costa saw familiar failings return for the Blues as they slipped behind against the high-flying Hornets.
Troy Deeney drew the visitors level from the penalty spot in the 42nd minute, before Odion Ighalo made it 2-2 on 56 minutes following an assist from Jurado.
The Nigerian has been one of the stars of the Premier League season so far, building on his terrific campaign in the Championship to bag 12 goals in 17 games for Vicarage Road outfit ahead of this clash.
His second looked to have set Watford up for an unlikely victory, as Chelsea began to squabble amongst themselves and lose the composure that had marked their recent triumph over Sunderland—the first match since the exit of Jose Mourinho.
However, new coach Guus Hiddink has clearly prompted an improvement from Costa, who bagged a second in the 65th minute—following an assist from the sublime Willian—to draw the Blues level.
While the west London heavyweights may not be able to find the winner against an excellent Watford side, Hiddink will at least be encouraged by the return to form of the gnarling Costa.
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