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.

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