Second half strikes from Willian, Loic Remy and Kurt Zouma broke the dogged resistance of plucky Watford as the Blues overcame their Championsip opponents 3-0 at Stamford Briidge in the FA Cup 3rd Round.
Make no mistake, for the first half, Watford while, never seriously threatening Peter Cech in goal, still held up the march of the Blues.
Only the double half-time change by Jose Mourinho, which saw the introduction of Diego Costa and Willian, did the west Londoners look like the side that tops the premier League.
The Blues almost scored on seven minutes when a pacy, in-swinging free-kick by Andre Schurrle was back-heeled by Gary Cahill. Unfortunately for the centre-back the lopping effort just inched over Watford goalkeeper Jonathan Bond's crossbar.
The Blues, naturally dominated the opening exchanges in terms of possession, with the visitors content to sit back with six or seven men camped on the edge of their penalty area.
Oscar was dumped unceremoniously on the ground by a hefty challenge by Bond on 15 minutes when he was chasing a deep Mikel through-ball. Watford, while not creating chances seemed content to allow the home side to keep possession. Every now and then a misplaced pass by a Chelsea midfielder would prompt the visitors to venture into the final third territory. Inevitably the move would break down and normal service would resume.
Chelsea forced Bond into a point-black save on 28 minutes when Loic Remy cut back the ideal right-sided byline cross for Didier Drogba. The ex-Ivory Cost striker met the ball with a strong header, despite the robust challenge of Gabriele Angella. But Bond was equal to the close-range downwards effort and snaffled the ball before it crossed his goal line.
Three minutes from the break and Watford held on again as a deep Luis corner was glanced on by Drogba but inched past Bond's right post.
A snatched Fernando Forrestieri shot was deflected for a corner -the first for Watford amounted later.
Jose Mourinho decided that the lacklustre forest half needed a major shakeup and so he decided to bring on Diego Costa and wide man Willian, for the ineffectual Oscar and out of sorts Schurrle.
That meant that Chelsea had all three front line strikers on at the same time.
An increase in urgency and tempo from the home side was in evidence from the kick off. But it was Watford who had the best chance of the restart, on 54 minutes when Troy Deeney sent in a low drive that Odion Ighalo got a touch on. Thankfully Petr Cech got a touch on the goal-bound shot and touched it away for a corner.
A see-saw few moments allowed Chelsea to attack ken the counter and Bond made a double saw from Drogba.
The visitors resolve was finally broken by a piece of exquisite finishing on 59 minutes.
Substitute Costa collected the ball on the left side edge of the Watford penalty area before touching it on to Remy. The Frenchman was upended but before any foul could be given, the ball was tapped onto the other substitute Willian.
The Brazil wingman took one touch of the ball before curling the perfect right-footed drive high and wide of the hapless Bond from outside the area to give the home side a deserved lead.
Watford boss and ex-Chelsea midfielder Slavisa Jokanvic decided to bring on Matej Vydra for Ighalo on 65 minutes.
Sighs of relief echoed round the 41,010 crowd five minutes later as Chelsea's superiority broke the resistance of the Watford argued once again.
Willian and Costa conspired to get the ball to Drogba who back-heeled it into Costa's path. The striker's shot was charged down but up popped Remy to thunder home a venomous right-footed volley past Bond.
Watford's FA Cup dream was finally extinguished a couple of minutes later when a simple clipped pass from Cesar Azpilicueta was met full on the head by centre-back Kurt Zouma who rose, unchallenged inside the visitors' penalty area and guided the ball past Bond with consummate ease.
Vydra unleashed a powerful drive from 20-yards which Cech did well to tip over his crossbars the visitors went in search of a consolation goal.
Nathan Ake replaced Drogba with 10 minutes to go as Mourinho, with the game won, effectively re-shaped his side to a more restraining one, intending to see the remaining minutes out with a minimum of fuss.
Costa could have had a fourth in the dying minutes but, from his curling 25-yard free kick, Bond managed to get a fingertip to the ball and nudge it onto his right post where it was quickly cleared from danger.
With the job done, the Blues counted down the minutes successfully and now await the 4th Round draw tomorrow evening.
Teams: Chelsea, Cech, Luis, Zouma, Ramires, Oscar, Drogba, Mikel, Schurrle, Remy, Cahill, Azpilicueta
Subs, Courtois, Ivanovic, Ake,Salah, Costa, Matic, Willian
Watford, Bond, Munari, Angella, Tozser, Deeney, Forestieri, Paredes, Cathcart, Pudil, Ighalo, Hoban
Subs, Gilmartin, Doyley, Murray, Vydra, Abdi, Doherty, Smith
Referee, Kevin Friend