Champions Chelsea have suffered an embarrassing home defeat to open their Premier League season, having two men sent off as unfancied Burnley beat them 3-2 at Stamford Bridge.
Antonio Conte's disjointed side struggled from the early stages when captain Gary Cahill was dismissed for a lunging tackle and they found themselves 3-0 down at halftime to a team who had not won at the ground since 1971.
Wales international Sam Vokes scored two of the goals and Stephen Ward the other.
New signing Alvaro Morata from Real Madrid came on to pull one back midway through the second half and then provided an assist for David Luiz, but in between midfielder Cesc Fabregas was also sent off for a second yellow card.
It was a dispiriting afternoon for Conte, who won the title in his first season at the club and wants more reinforcements.
"I am not worried, I am ready to fight with these players," he said. "Our fight in the second half was very good. But first half after the red card we lost our heads."
Liverpool manager Jurgen Klopp protested that Watford's stoppage-time equaliser by Manuel Britos in an entertaining 3-3 draw should have been disallowed for offside.
"We were unlucky in the end," Klopp said. "The equaliser was offside. It's obvious because the linesman is on the line. He needs to see it."
After the opening game of the season on Friday between Arsenal and Leicester City produced seven goals, Vicarage Road saw a similar level of entertainment - including some poor defending.
The home side, under new manager Marco Silva, led twice through Stefano Okaka and Abdoulaye Doucoure but Sadio Mane and Roberto Firmino, with a penalty, both equalised.
Debutant Mohamed Salah seemed to have won the points for the visitors before Britos's dramatic late intervention.
Life in the Premier League has got off to a flying start for Aaron Mooy and Huddersfield Town while Mat Ryan's Brighton suffered a reality check at home to Manchester City.
Mooy's Huddersfield travelled to London for their first top-flight clash in almost five decades and came away with three points after a 3-0 win over Crystal Palace.
The Terriers showed few signs of their long absence from England's top table, dominating Palace in the early exchanges.
Mooy showed the toughness that earned him player of the season honours in the Terriers' promotion campaign, highlighted by a challenge on Luka Milivojevic which set up his side's best chance of the first 20 minutes as Tom Ince attacked down the left.
Two minutes later Mooy set up Huddersfield's first-ever Premier League goal with a short corner to the near post. The subsequent flick-on led to an own goal from Palace defender Joel Ward.
It didn't take long for the visitors to double the advantage and Mooy was again in the thick of it. The former Wanderers and Melbourne City linchpin delivered a pinpoint cross in the 25th minute to find record signing Steve Mounie, who buried the header to make it 2-0.
Mounie put the icing on the cake with a second goal in the 78th minute.
On the south coast fellow new boys Brighton showed some encouraging signs before Manchester City's class shone through for a 2-0 win.
Socceroos gloveman Ryan was kept busy in the opening term but the title favourites were unable to break through. Brighton even looked the more likely to score 10 minutes after the break when City's goalkeeping woes appeared to rear their head once more.
With the home crowd in full voice, however, they were unable to capitalise and it was Sergio Aguero who finally broke the deadlock on 70 minutes before a Lewis Dunk own goal sealed the points five minutes later.
Wayne Rooney scored on his return to Everton from Manchester United to give the Merseysiders a 1-0 victory at home to Stoke City. It was his 199th Premier League goal and first for Everton since 2004.
"To score at Goodison on my first game back in the Premier League, it doesn't get much better," he said.
Egyptian defender Ahmed Hegazi, on loan to West Bromwich Albion from Al Ahly, scored on his debut in the 1-0 win at home to Bournemouth.
Elsewhere on the south coast Southampton and Swansea played out a scoreless draw.