Huddersfield Town, fifth in League One, were holding the runaway Premiership leaders to a 1-1 draw at Stamford Bridge in the third round of the FA Cup.
But such is the extreme depth in talent of Chelsea even on the bench, that the Blues clinched a spot in the next round thanks to a classic piece of counter-attacking play.
With The Terriers having leveled Carlton Cole's 12th minute strike, Eidur Gudjohnsen, the Icelandic striker turned into a midfielder at Chelsea by Jose Mourinho, found himself in the perfect position eight yards out to tuck home a smart right footer in the 82nd minute.
It was probably a just result, but having missed numerous chances and totally dominating play, Chelsea could easily have found themselves heading up the motorway to play a replay.
Worst case scenario would have been to suffer a late, late goal and defeat.
Chelsea's recent success owes much to their tremendous team spirit and the Huddersfield players demonstrated it in equal measure.
They came to Stamford Bridge to try and unsettle the Blues and grab an early goal and within 90 seconds of the start almost got that dream goal.
Gary Taylor-Fletcher took advantage of a Robert Huth error and sent in a low, left footed drive from six yards out. Chelsea's second-string goalkeeper Carlo Cudicini was alive to the situation and managed to smother the ball.
Chelsea made nine changes from their last Premiership tussle away to West Ham and one of them, Lassana Diarra, took full advantage to show Mourinho what he could do.
He had a fine right-footer on target on five minutes well saved by goalkeeper Philip Senior.
Shaun Wright-Phillips had several excellent chances to score during the game, the first he skied over the bar on six minutes.
But on 12 minutes, Chelsea took the lead.
Wayne Bridge sent in a low ball to the feet of Cole and the striker, playing his first match of the season, turned and shot in one quick movement.
The ball clipped into the air off the body of defender Martin McIntosh but Cole reacted quickest to nod the ball home over the advancing Senior.
From here on in Chelsea should have grabbed at least two more first-half goals.
Gudjohnsen, who blasted over the bar on two occasions, was the main culprit.
German centre-back Huth was unlucky not to have got his side's second five minutes from the interval. He looked on in despair as his headed effort from a Damien Duff corner ricocheted off the crossbar.
The second half saw Huddersfield do what many teams have failed to do at Stamford Bridge and score a goal.
With 15 minutes remaining, Nathan Clarke pushed forward, sliding the ball into the path of Taylor-Fletcher whose low, right-footer arrowed inside Cudicini's far post.
The shock was on but class finally told and Chelsea moved into the next round.
Chelsea - Lassana Diarra. On his first start the youngster dominated midfield play, breaking down attacks and setting them up.
Huddersfield – Mark Hudson. Reacted positively to the famous faces in front of him and caught the eye in the centre of the pitch.