Brighton staged a superb fightback from two goals down to beat Manchester City 3-2 after the champions had Joao Cancelo sent off, while Manchester United were held to a 1-1 draw by relegated Fulham as fans returned to the Premier League on Tuesday.
Supporters have been allowed back into Premier League matches this week for the first time since December.
A limited number of fans had attended the League Cup final and the FA Cup final in April and May respectively, as well as one of the FA Cup semi-finals.
All of those matches were staged at Wembley, but the Premier League had delayed the last two rounds of fixtures to take advantage of the UK's easing of coronavirus restrictions.
Around 7,900 saw Brighton's dramatic revival against City, with 10,000 United fans present at Old Trafford and 8,000 at Southampton for their 2-0 defeat against Leeds.
With the title wrapped up, City are fine-tuning their preparations ahead of the Champions League final against Chelsea in Porto on May 29.
But Pep Guardiola's side were beaten for the second time in their last three games after a second half collapse at the Amex Stadium.
Ilkay Gundogan headed City into the lead from Riyad Mahrez's second minute cross.
But Cancelo saw red in the 10th minute after the City defender hauled down Danny Welbeck.
Phil Foden increased City's lead in the 48th minute with a fine solo effort, only for Leandro Trossard to get one back moments later.
Adam Webster equalised with a thumping header in the 72nd minute before Dan Burn grabbed the winner from close-range four minutes later.
At Old Trafford, supporters were back for the first time since March 8, 2020, although several hundred broke into the stadium earlier this month in protest at United's owners the Glazer family and their role in the failed European Super League plan.
That ugly invasion and clashes with police outside prompted the postponement of United's match against Liverpool later the same day, while there were more protests before the rearranged game on Thursday.
The return of fans to Old Trafford was surprisingly peaceful despite fears of more disruption, although many wore green and yellow scarves in the colours of United's predecessors Newton Heath, which became a symbol of protests against the Glazers when they bought the club in 2005.
Some held up signs reading "Glazers Out" and chanted against the Americans, but the discontent was drowned out by songs of praise for Cavani in the 15th minute.
Bruno Fernandes flicked David De Gea's long ball into Edinson Cavani's path and the Uruguay striker, spotting Alphonse Areola off his line, lofted a gorgeous 40-yard chip over the Fulham keeper.
De Gea was back in goal in place of Dean Henderson in what could be the Spaniard's farewell appearance at Old Trafford amid reports he could leave in the close-season.
But De Gea was beaten in the 76th minute when Joe Bryan headed the equaliser from Bobby Decordova-Reid's cross.
Second placed United, now without a win in three games, suffered another blow ahead of the Europa League final against Villarreal on May 26 when Scotland midfielder Scott McTominay limped off injured.
United captain Harry Maguire is already racing to be fit for the final after suffering an ankle problem.
At St Mary's, Patrick Bamford ruined the return of Southampton fans as the Leeds striker slotted home in the 73rd minute.
Tyler Roberts bagged Leeds' second goal in the 90th minute to clinch the points for Marcelo Bielsa's side.
Later on Tuesday, Chelsea face a do or die clash with Leicester in the race to qualify for next season's Champions League via a top four berth.
Thomas Tuchel's fourth placed side are two points behind third placed Leicester, with both teams having two games left.
Leicester have already inflicted a painful blow on Chelsea after beating them 1-0 in the FA Cup final on Saturday.
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