Lionel Messi scored his first Paris Saint-German goal in the French club's 2-0 win over visiting Manchester City while Luxembourg midfielder Sébastien Thill struck late for Sheriff to stun 13-time champion Real Madrid in the Champions League on Tuesday.
Messi, who joined PSG on a two-year contract after leaving Barcelona, found the top corner superbly in the second half to add to Idrissa Gueye's early first-half opener and put the capital club top of Group A on four points.
Luis Suárez also struck late as his injury-time penalty gave Atlético Madrid a 2-1 win at 10-man AC Milan. Club Brügge and Liverpool also claimed away wins at Leipzig and Porto, respectively.
Messi scores maiden goal for PSG
After two games, City are third on three points after their first defeat in a group stage game since 2018 ended an 18-match unbeaten run, a point behind PSG and Club Brugge, who won 2-1 at RB Leipzig.
Real Madrid slumped to a 2-1 defeat by Moldovan side Sheriff Tiraspol in the Champions League on Tuesday as the visitors pulled off one of the biggest shocks in the competition's history with a stunning 89th-minute strike from Sebastien Thill.
Spanish champion Atlético were second best for long periods at Group B rival Milan. Luis Suarez's stoppage-time penalty and Antoine Griezmann's first goal since returning to Atletico Madrid earned the Spanish side a 2-1 victory over 10-man AC Milan in the Champions League on Tuesday.
On the other hand, Mohamed Salah and Roberto Firmino both struck twice and Sadio Mane once in a 5-1 drubbing of the Portuguese champions to seize control of Champions' League Group B.