Games are being played at the Estadio Antonio Coimbra da Mota – a 5,000-capacity ground in Estoril – but it was transformed for the World Sevens.
From 20:30 BST on Saturday, following Estoril men’s 4-0 win over Estrela, stands were built, TV cameras put in place and large screens put up.
The match schedule was shuffled after United’s men reached the Europa League final – which they lost 1-0 to Tottenham on Wednesday – so Skinner’s side played earlier at the World Sevens to avoid a clash.
Fans initially came in slowly, with little more than 100 watching City’s win over Rosengard, but alcoholic drinks were flowing as more came throughout the night, filling a stand on the far side before Paris St-Germain’s 2-1 win over Benfica.
“It is interesting. It is something different. The stadium looks nice,” said City fan Leanne Woodall, who travelled out to Estoril.
Fan Charlotte Wilkins added: “I play seven-a-side football so I was really excited to see how the professional players did it and the tactics they used.
“We couldn’t find where we needed to go when we first got here, but now we’re in, it’s really good and there’s good vibes so far. It’s exciting.”
Organisers hope to fill the arena on Friday when the semi-finals and final will be played and more fans fly out to Portugal in anticipation of Saturday’s Champions League final between Barcelona and Arsenal (17:00 BST).
But first impressions from the players were certainly positive.
“It was so nice, I was really sad it was only one game today, I could play all day like this,” said Roma’s Hawa Cissoko.
“I think we took the game a bit more seriously at the beginning than Manchester United, they arrived on the pitch really [relaxed].
“Them doing this made me think ‘we are here to have fun’. We were doing this when we were kids. It makes me feel a bit like [I did] 10 years ago. That’s so nice.”
Manchester City interim manager Nick Cushing said the style of football was how they “believe the game should be played”.
Brazil forward Kerolin added: “I liked a lot the music. In Portugal the weather is really nice so everyone is like ‘OK, we like these vibes’.
“Of course we want to win and get some money! But it’s a little bit Brazilian I think. I like the ginga [an informal Brazilian term for expression of creativity with agility and trickery].
“I want to get back those things and be a little bit brave. Today I was a little bit unsure – but it will come.”