Europa League specialist Radamel Falcao scored again Thursday as 2010 winner Atletico Madrid beat Celtic 2-0 in a group-stage opener.
Falcao scored 18 goals last season to help FC Porto succeed Atletico as champion, and persuade the Madrid club to pay $57 million for his offseason transfer.
The Colombia international took just three minutes to strike with a header from a corner, and Brazilian midfielder Diego put in a right-footed shot in the 69th minute.
UEFA will be asked to annul the result by FC Sion, which was expelled from the competition for fielding ineligible players in its playoff-round victory over Celtic. UEFA confirmed the Scottish club's place in the lineup on Tuesday.
Completing what is probably the toughest group, Udinese's talismanic forward Antonio di Natale scored in a 2-1 victory over Rennes.
Big-spending Paris Saint-Germain, expected to contend for the trophy, won 3-1 at home against Salzburg.
PSG led at halftime through Brazilian midfielder Nene, from the penalty spot, and Mathieu Bodmer. France midfielder Jeremy Menez, an $11.5 million offseason signing from AS Roma by the club's new Qatari owners, made it 3-0 before Salzburg got a late consolation goal.
Braga, beaten by Porto in the final last May, won 3-1 at English second-division side Birmingham, and last season's Champions League semifinalist Schalke earned a scoreless draw in Bucharest against Steaua.
Besiktas beat Maccabi Tel Aviv 5-1 in a match overshadowed by troubled Turkish-Israeli political relations. Maccabi players were booed before the match, and 2,000 police officers were deployed at the stadium in Istanbul.
Shamrock Rovers, Ireland's first representative in the group stage of a UEFA competition, lost 3-0 at home to Russia's Rubin Kazan after both teams had a penalty saved.
Tottenham fielded a team of reserves in Greece and earned a scoreless draw against PAOK, which missed a twice-taken penalty.
Stoke also took a point from a long away trip, though Dynamo Kiev got even 1-1 in stoppage time through Ognjen Vukojevic. Stoke led through Cameron Jerome's 55th-minute finish.
Fulham, which lost the 2010 final to Atletico, tied FC Twente 1-1 at home.
Lazio was reduced to 10 men when defender Luciano Zauri was dismissed in the 62nd minute, but still leveled for a 2-2 draw at home to Vaslui. Brazilian midfielder Wesley scored twice for the Romanian visitors.
Also on a 24-match program Thursday, Athletic Bilbao won 2-1 at Slovan Bratislava and Sporting Lisbon got a 2-0 victory at FC Zurich. PSV Eindhoven edged Legia Warsaw 1-0 and Anderlecht's Argentinian forward Matias Suarez got a hat trick in a 4-1 win over AEK Athens.
AZ Alkmaar beat Malmo 4-1. Jozy Altidore opened the scoring in the 21st minute before Rasmus Elm doubled the lead from the penalty spot. Adam Maher made it 3-0 at halftime.
