Paris - Juventus kicked off their Champions League campaign with a 2-0 victory at Valencia in a match overshadowed by a controversial red card for Cristiano Ronaldo, while tournament favourites Manchester City were stunned at home by Lyon on Wednesday.
Ronaldo's Champions League debut for Juventus lasted less than half an hour as the Portuguese star was red-carded after a collision with Valencia defender Jeison Murillo.
After tangling with Ronaldo, Colombian Murillo tumbled to the ground holding his face, and referee Felix Brych consulted with the assistant official beside the goal before giving the competition's all-time record goalscorer his marching orders.
But Juventus, who had totally dominated until Ronaldo's dismissal, were awarded two penalties within six minutes either side of half-time, and Miralem Pjanic confidently dispatched them both.
The Italian champions defended well thereafter to keep the hosts at arm's length, although Juve goalkeeper Wojciech Szczesny did save a Daniel Parejo spot-kick in the final minute of injury-time.
Manchester United top the early Group H table, though, after continuing their recent upturn in form by brushing aside Young Boys 3-0 in Bern to notch a third straight win in all competitions.
Jose Mourinho's men were inspired by Paul Pogba on the artificial pitch, as the French World Cup winner drilled home a brilliant opener before converting a penalty on the stroke of half-time.
Pogba completed a virtuoso individual display by sending Anthony Martial free to slot in his fourth Champions League goal for United in the 66th minute.
But English champions Manchester City struggled, with Pep Guardiola watching from the stands after a touchline ban, and were beaten 2-1 by French side Lyon at the Etihad Stadium after an error-strewn display.
City, the bookmakers' favourites for the title this season, suffered a nightmare first half against an enterprising Lyon, with Maxwel Cornet sweeping in after a mistake by Fabian Delph, and Nabil Fekir drilling home before half-time.
The introduction of Sergio Aguero as a substitute revitalised City after the break, and Bernardo Silva turned in Leroy Sane's cutback with 23 minutes still to play.
But Lyon, who have only won two of their first five Ligue 1 matches this term, held on to clinch a famous victory and ease the pressure on coach Bruno Genesio.
In the other Group F game earlier on Wednesday, Brazilian youngster Maycon came off the bench to rescue Shakhtar Donetsk a 2-2 draw in their game against group-stage debutants Hoffenheim in Kharkiv.
Paulo Fonseca's Ukrainian champions trailed twice, but the 21-year-old Maycon's thunderous left-footed strike in the 81st minute grabbed a point in the Group F clash.
Holders Real Madrid showed that they are still serious contenders on the biggest stage despite seeing Ronaldo leave for Juventus in the close season, as Julen Lopetegui's men saw off Roma 3-0 at the Santiago Bernabeu.
Isco curled home a sumptuous 45th-minute free-kick to give the 13-time champions the lead, before Gareth Bale made it three goals in two Champions League matches after his spectacular double in May's final win over Liverpool.
Mariano Diaz, making his second debut for Real after re-joining from Lyon last month, smashed home a fantastic third in added time.
Real next travel to CSKA Moscow on October 2, after the Russians came back from two goals down to salvage a 2-2 draw at Viktoria Plzen, with Everton loanee Nikola Vlasic scoring an injury-time penalty.
Five-time champions Bayern Munich got their Group E campaign off to a solid start as Niko Kovac's men eased to a 2-0 triumph against Benfica in Lisbon.
Robert Lewandowski put them ahead in the 10th minute, before Renato Sanches netted in the second half to score his first goal since returning to Germany after his miserable loan spell at Swansea.
Ajax cruised to a 3-0 victory over AEK Athens in Amsterdam earlier in the day to sit atop the early standings, with Argentinian Nicolas Tagliafico scoring twice.