Champions League: Liverpool rolls, Real Madrid and Manchester City suffer ugly defeats

While Liverpool took care of business at home with a comprehensive 4-0 win over Xabi Alonso-coached Bayer Leverkusen, Tuesday will be remembered mostly as a day of upsets in the UEFA Champions League.

Real Madrid lost 3-1 at home against AC Milan, Manchester City squandered an early lead and suffered an eye-popping 4-1 defeat to Sporting Lisbon (and future Manchester United manager Rúben Amorim) while Scottish club Celtic came from behind to top German Bundesliga rep RB Leipzig 5-1 in Glasgow.

Here are three quick takeaways from Tuesday's games as Matchday 4 kicked off.

AC Milan stuns Real Madrid at the Bernabéu

With 22 European titles between them, Tuesday's contest in the Spanish capital was a meeting between the competition's two most successful teams.

The hosts and current trophy holders still came in as the clear favorites despite their struggles in La Liga, including a 4-0 home loss to rival Barcelona last weekend. Meantime, AC Milan has had an up and down season of their own, both in the Champions League and in Italy's Serie A.

That's not how it played out at Estadio Santiago Bernabéu. The Rossoneri were the livelier team from the start, and sure enough the visitors took the lead after just 12 minutes. U.S. men's national team star Christin Pulisic helped set up the opener with an inch-perfect corner kick for Malick Thiaw to nod home from close range:

Madrid soon equalized from the penalty spot via Vini Jr. But Milan went ahead again before the half was over. Pulisic was heavily involved again. The American found Rafael Leão with a slick cutback pass in the buildup before former Real Madrid striker Álvaro Morata cleaned up the rebound from Leão's shot.

Tijjani Reijnders added an insurance goal for AC Milan in the second half. The loss dropped Real Madrid to 2-2 on the season, leaving the 15-time trophy winners 17th in the 36th-team league stage standings.

In Lisbon, Manchester City takes a rare drubbing

When Phil Foden put the English Premier League champs up 1-0 in Portugal a little more than three minutes into Tuesday's affair, it felt like the Sky Blues would roll. With nine goals scored through three games, Pep Guardiola's squad usually does. Instead, things went sideways for the guests in short order after Viktor Gyökeres leveled matters with a gorgeous finish later in the second half.

Maximiliano Araújo put Sporting up just after the intermission, and Gyökeres made it 3-1 from the penalty spot moments later. And while City had plenty of time to respond, they failed to use it. Gyökeres completed his hat trick from the spot to seal a famous win for his club with about 10 minutes of regular time remaining.

The defeat is Man City's third in a row across all competitions — its first three-game losing streak since 2018.

USMNT's Malik Tillman leads PSV rout

While the American midfielder has had a hard time getting starts for the national team since making his debut two years ago, Tillman's career season with Dutch champs PSV Eindhoven continued on Tuesday with a Man of the Match performance in a 4-0 drubbing of Spain's Girona.

The 22-year-old had a hand in three of the hosts' four tallies. After assisting on the opener, Tillman scored an incredible solo goal following a 40-yard-run out of midfield:

Tillman and Pulisic were two of nine Americans who appeared in Tuesday's matches. Yunus Musah also started for Milan. Cameron Carter-Vickers and Auston Trusty partnered in central defense for Celtic. Ricardo Pepi was a late sub for PSV, while Juventus pair Weston McKennie and Tim Weah also came off the bench in a 1-1 tie with Lille, Weah's former club.

Finally, 18-year-old Cole Campbell made his Champions League debut when he played the final 13 minutes of Borussia Dortmund's 1-0 victory over Austria's Strum Graz.

Doug McIntyre is a soccer reporter for FOX Sports. A staff writer with ESPN and Yahoo Sports before joining FOX Sports in 2021, he has covered United States men's and women's national teams at FIFA World Cups on five continents. Follow him @ByDougMcIntyre.