Aston Villa's relegation woes worsened as Troy Deeney's double helped 10-man Watford to a 3-0 win at Vicarage Road.
Deeney had put the hosts in front shortly before half-time in a one-sided opening period during which they enjoyed almost 65 per cent of possession and had 11 shots.
Mariappa's dismissal for a second yellow card in quick succession threatened to undo their good work, but instead they continued to dominate and increased the pressure on Villa, who remain a point inside the bottom three but have now played two games more than 17th-placed West Ham.
Rejuvenated Watford dismantle Villa
Watford, who themselves only picked up a first home win of 2019/20 last weekend, had all the confidence Villa lacked, and enjoyed almost total domination before the break, save for one shaky moment when Wesley should have beaten Ben Foster with a downward header, but directed his effort within reach for the goalkeeper to turn it over the bar.
Pearson would have worried Watford would not have the half-time lead their play deserved, especially when Deeney missed a fine chance from another corner four minutes before the interval, but he made amends moments later when Heaton palmed Doucoure's effort out wide, and the home skipper was fastest to react to scuff home the opener.
Dean Smith opted for a change at the break, introducing Anwar El Ghazi with hope of providing some new energy for the visitors, but the balance of play barely changed as Watford continued in full control.
That looked like changing when Mariappa was booked for the second time in a matter of moments by Simon Hooper although he did not make contact with Henri Lansbury for the latter, although any feelings of rough justice were soon washed away when Watford doubled their lead 10 minutes later.
Matt Targett went down with an injury in the Villa half but the visitors played on, and were caught out on the break when they lost the ball, Sarr's through-ball set Deeney free in the area, and a shove from Douglas Luiz sent him tumbling before he got up to convert from 12 yards.
Villa were undone again as they pushed for a comeback goal, with the ease of Watford's third perhaps the most worrying for Smith. Jack Grealish was tackled by Etienne Capoue on the half-way line. Deeney then slipped the Frenchman in down the left, and he crossed excellently to the far post where Sarr blasted home after a late run.
A bad-tempered affair descended into a flurry of needless yellow cards in the final minutes with the tension in both camps apparent, but Watford eased plenty of the angst around Vicarage Road come full time as they finished the week unbeaten, having almost doubled their season points tally in the last six days.
What the managers said...
Watford head coach Nigel Pearson: "They had the opportunity to put the ball out of play before the penalty. I've not actually seen the penalty, we have technology now, and I think it would be fair to say our players, over the course of the season, have not necessarily thought things have gone our way."
Aston Villa boss Dean Smith: "They go down to 10 men and you think you've got a really good chance of getting back in it. Then there's two goals that are comical.
"Matt Targett goes down with a hamstring injury for the second, Jack [Grealish] is on the ball, he doesn't know, keeps playing, Watford win the ball, play on and get a penalty. I've seen the replay back, it's shoulder to shoulder. Troy goes down very easily. If that goes back to VAR, it's a mistake. If the referee's allowed to walk over to a screen which is 30 yards away, and looks at the screen, he'll say sorry, I've made a booboo.
"The third goal is a foul right in front of me. Whether they've got the protection of saying we can still go back if they score under VAR, it's a foul. The lad goes through the back of Jack. There's been free kicks all game for things like that, with [Ismaila] Sarr going down, but forget the second half, we lost the game in the first half today because my players weren't good enough."
Man of the match - Troy Deeney
Watford have missed their talisman this season, but since his return at the start of the month he has gradually got back to his best and his brace was crucial in their vitally important win.
He was at his typical, battling best by taking on 22 duels, the most of anyone on the pitch, and most importantly netted twice, making his second himself, to give Watford a big helping hand towards three points.
Match facts
- Watford have won seven points in their last three Premier League games (W2 D1), as many as they had from the previous 12 matches (W1 D4 L7).
- Nigel Pearson has won seven points in his four games as Watford manager - only one manager has picked up more points in their first four Premier League matches in charge of the Hornets (Marco Silva - eight).
- Aston Villa have won fewer points on the road than any other side in the Premier League this season (4).
What's next?
Both sides are back in action on New Year's Day, with Aston Villa travelling to Burnley in the 12.30pm kick-off, and Watford hosting Wolves at 3pm.