Arsenal edged past Udinese 1-0 at The Emirates in the first leg of their Champions League qualifying tie.
Theo Walcott's fourth-minute goal was the difference between the sides; the England winger meeting Aaron Ramsey's cross with a neat finish at the near post.
But it was far from a convincing performance from Arsene Wenger's team, who were threatened on numerous occasions by the Italian visitors. Antonio Di Natale hit the bar with a free-kick, and came close again following up a sharp save from Pablo Armero's effort.
In the second half Udinese looked to capitalise on the home side's nerves. Di Natale was once again to the fore and only a desperate tackle from Johan Djourou denied him an equaliser. At the other end, Arsenal could have grabbed a second themselves late on when Walcott saw his curling shot superbly saved by Samir Handanovic in the Udinese goal.
Dutch side Twente Enschede were held to a 2-2 draw at home to Portuguese champions Benfica.
Twente went ahead early through Luuk de Jong, before the visitors turned the tie around with goals from Oscar Cardozo and Manuel Nolito before halftime. The home side found an 80th-minute equaliser through Bryan Ruiz.
Lyon enjoyed a 3-1 first leg victory over Russian side Rubin Kazan at the Municipal De Gerland.
Vladimir Dyadyun gave the visitors an early lead on three minutes, but the French hosts repied through Bafetimbi Gomis and went ahead with an own goal from Solomon Kverkvelia. Jimmy Briand gave Lyon a two-goal cushion on 71 minutes.
Czech champions Plzen had a notable 3-1 victory away to FC Copenhagen of Denmark.
A Solvi Ottesen own goal put the visitors ahead on 52 minutes, with Vaclav Pilar doubling their lead soon after. Copenhagen replied through Solvi Ottesen, but Plzen midfielder Martin Fillo made it 3-1 to make the Czech's strong favourites to go through to the Champions League proper.
Bate Borisov came from a goal behind to draw 1-1 at home to SK Sturm Graz.
The Austrian visitors went ahead through Manuel Weber on 12 minutes, but Marko Simic's 59th-minute equaliser will see the Belarus champions in the second leg on level terms.