Barcelona's 2-0 win over Benfica came at a huge cost, with captain Carles Puyol carried from the field with a suspected broken arm and star midfielder Sergio Busquets shown a straight red card.
Goals either side of half-time to Alexis Sanchez and Cesc Fabregas helped the Catalan giant remain unbeaten in its opening two Group G matches, but the evening took a turn for the worse when Puyol was carried off on a stretcher with what appeared to be a broken arm after he landed awkwardly when attacking a corner.
(Carles Puyol is taken from the field as Tito Vilanova watches on. ACTION)
Busquets was shown a contentious straight red card two minutes from time which will rule him out of the next two matches, barring a successful appeal by the club.
The shock of the day was BATE Borisov claiming the biggest scalps in its history after stunning in-form Bayern Munich 3-1 at the Dinamo Stadion to open up a three-point lead at the top of Champions League Group F.
Goals Alexander Pavlov and Vitaly Rodionov put the Belarusian champion in charge and although Bayern pulled one back in stoppage time through Franck Ribery, BATE added a third through Renan Bressan to seal a first ever home win in the competition.
The victory means unfancied BATE has won both its group matches having previously downed Lille 3-1 away, while for Bayern the defeat ends a nine-match winning streak at the start of the season and leaves it on three points in Group F.
Valencia got its UCL campaign up and running as two goals from Jonas sealed a 2-0 win over Lille.
European champion Chelsea claimed its first win of this year's competition after seeing off Nordsjaelland 4-0 in Group E.
Roberto Di Matteo's men were made to work hard for their triumph at the Parken Stadium in Copenhagen, and they only sealed victory with three goals in the last 11 minutes as their Danish opponent ran out of steam.
Juan Mata notched his third goal in as many games and added the third after a superb free-kick from David Luiz before Ramires completed the scoring.
The Blues now top the group after Juventus was surprisingly held to a 1-1 home draw by Shakhtar Donetsk.
It took a thunderbolt from defender Leonardo Bonucci to guarantee a share of the spoils after Alex Teixeira had put the Ukrainian side ahead on the counter-attack.
A late Georgios Samaras header earned Celtic a 3-2 Group G victory over 10-man Spartak Moscow in the Luzhniki Stadium.
Striker Gary Hooper gave the visitor the lead in the 12th minute before Emmanuel Emenike netted either side of the break, but after Spartak defender Juan Insaurralde was sent off, the tide changed in Celtic's favour.
It levelled in the 72nd minute when substitute James Forrest's strike deflected off Dmitri Kombarov and Samaras capped a remarkable night for the Hoops after heading in Emilio Izaguirre's cross seconds after the regulation 90 minutes.In Group H, Robin van Persie scored his first Champions League goals for Manchester United, which came from behind to beat CFR Cluj 2-1.
Greek forward Pantelis Kapetanos had put the Romanian champion in front in the 14th minute but United went three points clear at the top thanks to Van Persie's strikes either side of the interval, his second a sublime finish from an inch-perfect Wayne Rooney ball.
Galatasary was made to pay for poor finishing as a 27th-minute goal from Ruben Micael and a last-gasp effort from Alan gave Braga a smash-and-grab 2-0 win.
Matchday 2 Results
FC Nordsjaelland 0-4 Chelsea
Juventus 1-1 Shakhtar Donetsk
BATE Borisov 3-1 Bayern Munich
Valencia 2-0 LilleGroup G
Spartak Moscow 2-3 Celtic
Benfica 0-2 BarcelonaGroup H
CFR Cluj 1-2 Manchester United
Galatasaray 0-2 Braga