Raheem Sterling scored twice to deepen managerless Watford's relegation fears as Manchester City recorded a resounding 4-0 win at Vicarage Road.
Sterling's first-half double put City in control, with his superb opener (31) added to when he slotted home the rebound after Ben Foster saved his initial penalty (40).
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Phil Foden grabbed City's third in the 63rd minute to better his goal tally of seven from last season before Aymeric Laporte headed in a simple fourth as the hosts capitulated (66).
In this absorbing race for survival, Watford later slipped into the relegation zone on goal difference with Aston Villa's 1-0 win over Arsenal enough to move them out of the bottom three.
Pep Guardiola's City side, already assured of second place, secured a fourth consecutive league win for the first time this campaign to move onto 78 points to help erase the memory of Saturday's FA Cup semi-final defeat to Arsenal.
How City kept Watford in perilous position
Watford remain in the thick of the relegation battle. Friday's 3-1 defeat at West Ham - and a "frank exchange" with the owner Gino Pozzo - cost Nigel Pearson his job over the weekend.
Having been placed as interim head coach for the second time this season, this always looked an intimidating prospect for Hayden Mullins; City entered the game on a 12-game winning run against Watford, scoring 46 goals in those matches - including an 8-0 win at the Etihad back in September.
The visitors effectively had nothing to play for, assured of a spot in next season's Champions League, but having enjoyed 88 per cent possession inside the opening 10 minutes, it was Watford who had the game's first chance as Will Hughes dragged a shot wide from the edge of the box following a poor clearance from Joao Cancelo.
But City very nearly took the lead moments later when Bernardo Silva found Rodri in space 30 yards out, and his speculative drive looped off the back of Gabriel Jesus and forced Foster into a fine one-handed save.
Guardiola's men were 5-0 up after 18 minutes the last time they played Watford - but they found themselves being frustrated as Foden's deflected shot wide of the post was the closest they came to breaking the deadlock prior to the first drinks break.
The pause favoured City, and Watford's resistance was finally broken when Sterling superbly controlled Kyle Walker's pass before smashing home to leave Foster with no chance.
"He's not known for being the purest striker of a football, but he won't hit a better one," Jamie Redknapp said at half-time.
City's slickness opened Watford up once more before the interval as Sterling was tripped in the area by Hughes. The England international took the spot-kick himself, and after Foster denied him from 12 yards with a wonderful save to his right, the rebound dropped kindly for the City forward to tap in his 29th goal of the season.
By now, it was a case of damage limitation for the Hornets, but they played themselves into trouble immediately upon the restart as a poor back pass from Roberto Pereyra led to Foster keeping out Jesus' strike before the veteran goalkeeper was alert to prevent Sterling from completing his hat-trick by tipping over his rising shot all inside the opening two minutes of the second period.
Troy Deeney had denied reports of a fight in the Watford dressing room during half-time of that defeat at West Ham - but Foster was forming a one-man barrier as he kept out a brilliant Kevin De Bruyne free-kick on the hour-mark.
Two goals in the space of four minutes compounded the hosts' misery, however, as, after Foster kept out Sterling's initial effort, the ball broke loose for Foden to tap in his eighth goal of the campaign. The hosts were by now looking sorry for themselves, and De Bruyne's free-kick was headed home unmarked by Laporte with a third of the match still to play.
Ederson had been a spectator all game, but he was finally called into action with 12 minutes remaining as the Brazilian raced from his line to smother the ball at Danny Welbeck's feet - but there would be no consolation, the only respite for Watford being Jesus' stoppage-time header ruled out for offside.
There might have been a late fifth for City when Jesus rose to head in Cancelo's cross but the Brazilian was correctly flagged offside, a call that could well prove significant in the final reckoning - and Villa's win over Arsenal means Watford's fate is no longer in their hands.
What the managers said...
Watford interim boss Hayden Mullins: "We knew they were going to offer a reaction from the game at the weekend against Arsenal. We knew they would come here with a bit of a point to prove and we knew they wouldn't roll over. The first goal came at a time when we were just getting back after the water break so it was difficult to concede at that time.
"I thought Will Hughes got a touch on the ball for the penalty so that was tough to take, especially just before half-time. We'll reflect on this game tomorrow and we'll get the boys ready for the game on Sunday.
"We can't be thinking of Arsenal having one eye on the FA Cup final. We can only concentrate on ourselves rather than other results going our way. We played against a really good side tonight."
Man City boss Pep Guardiola: "It's important for Raheem to score goals but we cannot forget that we finished a long way off the champions. The distance from second to first is big and the distance between second and third is big too but it's not enough.
"Against Southampton we created a lot of chances and we lost. The most important thing is to finish games with the sense that we've done everything. We all still need to know that we are far away from Liverpool. This was the first time we've managed to win four in a row in the league. Two seasons ago, we managed 18, last season we managed 14.
"This happened because something was wrong, and I need to discover what it was ahead of next season."
Man of the match - Rodri
Sterling's goals will grab the headlines, but Rodri bossed this game in the middle of the park, completing more passes (65) than the entire Watford team in the opening half (55).
The precision in his distribution continued in the Hertfordshire summer sunshine as he completed 125 of his 131 passes. The 24-year-old also made more tackles (4) and regained possession (11) more times than any of his team-mates.
"He's been unspectacular but really efficient with his passing," Alan Smith said on commentary to Sky Sports. "Where he did do well was competing with Troy Deeney in the first half, standing in front of the big centre-forward. It's been a really good performance."
Guardiola said: "Rodri came from an important club in Spain and it's not easy to adjust quickly to this league. He's going to learn and learn. I'm really happy with him."
Opta stats - City continue Hornets dominance
- Manchester City have scored 12 goals against Watford in the Premier League this season without conceding once - this goal difference of 12 over the two fixtures is the largest in the top-flight since 1947-48 when Arsenal also scored 12 without reply against Grimsby Town.
- Manchester City have scored 12 goals against Watford in the Premier League this season, a joint-record for most goals against an opponent in a single campaign in the competition alongside Blackburn vs Nottingham Forest in 1995-96 and Spurs vs Wigan in 2009-10.
- Since Watford returned to the Premier League in 2015-16, they have conceded 37 league goals against Manchester City, at least seven more than any side has conceded against another in this fixture in this time.
- Manchester City midfielder Kevin De Bruyne registered his 19th league assist of the season, equalling Mesut Ozil in 2015-16 and going just one behind Thierry Henry's league record of 20 in 2002-03.
- Manchester City forward Raheem Sterling has scored 10 goals against Watford in all competitions, only netting more against Bournemouth (11). He has scored nine goals in his last five matches against the Hornets.
What's next?
Watford travel to face Arsenal at the Emirates on the final day of the season this Sunday, while Manchester City host Norwich, with both games kicking off at 4pm.