Dennis Bergkamp scored the winner as Arsenal snatched a dramatic late win over Champions League minnows FC Thun.
Bergkamp struck late in injury-time, eluding Ljubo Milicevic before slipping the ball past Eldin Jakupovic.
Robin van Persie had earlier been given a straight red after catching Alen Orman in the face with his boot.
Gilberto then headed Arsenal in front while Thun equalised shortly afterwards when Nelson Ferreira's cross-shot looped over Manuel Almunia.
It was a dramatic escape for Arsenal after a largely frustrating 90 minutes.
Arsenal, even without the injured Thierry Henry, were expected to brush aside their modest opponents, who eight years ago were playing non-league football.
And the home team - with Sol Campbell making his first start of the season - created plenty of early chances, going close twice inside the opening 15 minutes.
Van Persie should have done better but shot straight at Eldin Jakupovic, while the Thun keeper did well to save a free-kick from Toure.
Shortly afterwards Jakupovic made a double save, denying Van Persie from a tight angle after he had initially spilled a long-range effort from Jose Antonio Reyes.
But despite dominating possession, Arsenal's intricate play often found its equal in Thun's dogged defence.
And the home crowd's frustration quickly became evident as the Gunners needlessly gave the ball away time and again.
It was sloppy play from the home team that gifted the ball to Pimenta Adriano, whose low strike brought out a decent save from Almunia, keeping goal in place of the suspended Jens Lehmann.
Jakupovic let a shot from Robert Pires embarrassingly squirm through his legs and was fouled by a sliding Freddie Ljungberg as he tried to retrieve the ball on the line.
But the opening half's real moment of drama came when referee Gregorz Gilewski handed Van Persie a straight red after he caught Alen Orman in the face with his boot.
Van Persie raised his foot while jumping for a header and appeared to be looking at the ball as he caught Orman in the face, with the Thun player sustaining a nasty gash on his forehead.
Gilberto headed Arsenal in front from a corner shortly after the restart before the Swiss side equalised through Ferreira's spectacular effort.
A deep cross fell to Ferreira, who seemed to have little on and defeated Almunia with a hooked effort that appeared to be more of a cross than a deliberate effort to score.
Minutes later a deflected cross then broke to Tiago Bernardi but, instead of stunning the Highbury crowd with another goal, he shot well over from 14 yards.
Arsenal's frustration reached boiling point close to the final whistle when a stray elbow caught Gilberto in the face, causing a painful cut above the eye, and Toure headed wide with the goal gaping.
But substitute Bergkamp, wrong footing Thun's defence with a sublime backheel, spared Arsenal's blushes with his late, late winner from six yards.
Arsenal: Almunia, Lauren, Toure, Campbell, Cole, Ljungberg (Hleb 80), Silva, Fabregas (Bergkamp 72), Pires, Reyes (Owusu-Abeyie 80), Van Persie.
Subs Not Used: Poom, Song Billong, Clichy, Senderos.
Sent Off: Van Persie (45).
Goals: Silva 51, Bergkamp 90.
FC Thun: Jakupovic, Orman, Hodzic, Milicevic, Goncalves, Gerber (Leandro 72), Bernardi, Adriano (Gelson 57), Aegerter, Ferreira, Lustrinelli (Faye 87).
Subs Not Used: Portmann, Duruz, Spadoto.
Booked: Hodzic, Goncalves, Ferreira.
Goals: Ferreira 53.
Ref: Grzegorz Gilewski (Poland).