Not even another free kick masterpiece from Dimitri Payet could inspire West Ham United in their push for a Champions League spot as they had Cheikhou Kouyate sent off in a 2-2 draw with Crystal Palace.
At the other end of the table, Aston Villa's disillusioned fans made a long, loud protest as their side were humiliated 4-0 at home to Chelsea and now stand on the verge of relegation.
Newcastle United are hot favourites to join Villa in the Championship next season after going down 3-2 in a dramatic clash at fellow strugglers Norwich City who ended up celebrating a 93rd-minute winner from Martin Olsson.
Newcastle's north-east rivals Sunderland are also in deep trouble, four points adrift of safety after a goalless home draw with West Bromwich Albion.
After losing three home games in a row, Arsenal rebounded to dominate Watford, who had knocked them out of the FA Cup at the Emirates Stadium last month, with Alexis Sanchez, Alex Iwobi, Hector Bellerin and Theo Walcott all on target.
Arsenal manager Arsene Wenger, who singled out the exciting young Nigerian Iwobi for more praise, said the performance had “brought a lot of belief back” to his side.
On the subject of whether the Gunners were still realistically still in the title hunt, he told Sky Sports: “It doesn't matter how realistic our title challenge is, we can only believe in our own game. We just continue”.
Manchester City had lost four of their last six games but stopped the rot with a blistering start at Bournemouth, Fernando, Kevin de Bruyne and Sergio Aguero scoring within 19 minutes.
Aleksandar Kolarov added the fourth in the dying seconds.
Arsenal are third, eight points behind leaders Leicester City and three adrift of Tottenham Hotspur who are playing at Liverpool in Saturday's late game.
Manchester City are four points behind Arsenal in fourth, with West Ham three adrift of Manuel Pellegrini's side in fifth after the Hammers' draw with Palace left manager Slaven Bilic frustrated again.
West Ham had come from a goal down to lead with goals from Manuel Lanzini and another glorious set-piece 20-metre strike from Payet but the game changed when Kouyate was sent off for fouling Dwight Gayle who scored the equaliser eight minutes later.
“I would love to say a lot of things, I asked the legal people what can I say and what I can't. It is never a red card and it's the fourth game in a row we are getting decisions that are costing us,” Bilic told the BBC.
The most dramatic action came in the relegation dog-fight at Carrow Road when Aleksandar Mitrovic looked set to be Newcastle's hero again.
He followed up his equaliser against Sunderland two weeks ago with two more goals, including an 86th-minute penalty which looked set to earn his side a point.
Yet Norwich, who had led twice through Timm Klose and Dieumerci Mbokani, were not to be denied, with Swedish full back Olsson racing through to hit the winner with a low drive three minutes into added time.
Villa's woes continued with a pitiful performance and a seventh straight league defeat, leaving unhappy fans to hold up banners in protest and begin walking out of Villa Park after 74 minutes following Chelsea goals from Ruben Loftus-Cheek, on-loan Brazilian international Alexandre Pato and two from Pedro.
Original source: Arsenal, City keep up pressure in title race