A much-changed Manchester United team could only draw 0-0 with Rangers in their opening Champions League tie as Antonio Valencia suffered what appeared to be a serious injury. Meanwhile, Tottenham let slip a two-goal lead to draw with Werder Bremen.
United made ten changes from the side that drew with Everton at the weekend and failed to carve out enough chances at Old Trafford when being frustrated with a defensive Rangers side.
Midfielder Valencia was taken to hospital after suffering what appeared to be a broken leg in the second half following a challenge from Kirk Broadfoot. The Ecuadorian required oxygen on the pitch and television broadcasters did not show replays of the incident.
Tottenham's first ever Champions League game started superbly when an own goal from Petri Pasanen and a towering header from Peter Crouch put them 2-0 up against Bremen, but they were held to a 2-2 draw in Germany.
The German side responded in four second-half minutes as Hugo Almeida and the excellent Marko Marin drew the hosts level. Almedia scored with a header after 43 minutes and Marin fired home a low effort soon after.
Also in Group A, Rafael Benitez had an unconvincing beginning to his Inter Milan career in Europe as his side were held to a 2-2 draw by FC Twente.
The visitors opened the scorer when Sneijder drilled his shot into the bottom-right corner of the FC Twente goal, but Twente were quickly back on level terms when Theo Janssen scored.
There was only half an hour on the clock when Twente completed the comeback by taking the lead in fortuitous circumstances as an inswinging corner from right by Janssen was head into his own goal by Argentinian forward Diego Milito. But Samuel Eto'o drew things level once more when he struck just before half-time.
A Lionel Messi-inspired Barcelona recovered from the shock of going a goal down against Panathinaikos to get their Champions League campaign off to a convincing start at Camp Nou with a 5-1 victory.
Panathinaikos took the lead against the run of play through Sidney Govou in the 20th minute but Barca hit back in merciless fashion to take a 3-1 lead by half-time through two goals from the irrepressible Messi and another from David Villa.
Messi, having also hit the crossbar in the first half, spurned the chance to net his hat-trick in the 55th minute when his weak penalty was saved by Alexandros Tzorvas, but teed up Pedro and Daniel Alves for further goals.
Benfica put their poor domestic form to one side as they opened their Champions League Group B campaign with a comfortable 2-0 win at home to Hapoel Tel Aviv.
Jorge Jesus' Portuguese champions have lost three of the opening four matches in the Liga but were on course when their Brazil defender Luisao scored after 21 minutes. Oscar Cardozo then added a second after 69 minutes to seal the points against a Hapoel side making their first appearance in the group stage.
Valencia kicked off their Champions League Group C campaign with a thumping 4-0 away win in Turkey against Bursaspor. The Spanish side go top of the group ahead of Manchester United.
Bursaspor beat Istanbul giants Galatasaray, Besiktas and Fenerbahce to win their domestic title last season but had no answer against the Spanish Primera Division side. Facundo Costa and Aritz Aduriz scored in the first half and Pablo Hernandez and substitute Roberto Soldado added a deserved coat of gloss after the interval.
Lyon got their Champions League campaign off to a winning start with a 1-0 victory over Schalke but they had Benedikt Hoewedes to thank.
The Schalke defender put through his own net under pressure from Michel Bastos on 21 minutes and was then sent off in the 38th minute for a professional foul on Jimmy Briand.
Senegal striker Dame N'Doye served up a potentially priceless winner three minutes from time as FC Copenhagen recorded a 1-0 victory over Rubin Kazan in the Danish capital.