• Olympiacos's Arthur Masuaku opens the scoring with a sensational strike
• Ibrahim Afellay doubles the advantage after Alejandro Domínguez's determined run
• After near misses, Mario Mandžukić pulls one back on his competition debut for for Atlético
• Kostas Mitroglou breaks his ten-month goal duck with the third for the hosts
• Substitute Antoine Griezmann hits back for Atlético from close range
Olympiacos FC pulled off one of the shocks of matchday one with a 3-2 Group A victory over last season's runners-up Club Atlético de Madrid in Piraeus.
Arthur Masuaku gave the Greek title-holders a dream start after 13 minutes when he drilled in a low shot on his UEFA Champions League bow and the visitors were stunned further when the hosts doubled their lead through Ibrahim Afellay just after the half-hour. Mario Mandžukić reduced the deficit seven minutes before half-time, but the visitors were hit by Kostas Mitroglou's 73rd-minute sucker-punch – his first goal for ten months. Although Atlético substitute Antoine Griezmann set up a breathless finish with a late close-range effort, Míchel's men hung on for a remarkable win.
It took 13 minutes for the first real opportunity and it brought a goal for the home team. Alejandro Domínguez’s short corner was laid off to Masuaku by Afellay and the French left-back, 20, beat Jan Oblak with a sensational low strike from just outside the area. Atlético coach Diego Simeone, serving a touchline ban, showed no emotion from the stands and, far from being cowed, Atlético seized control. Mandžukić – twice – and Raúl García went close with three headers in six minutes. Then, against the run of play, Olympiacos stunned Atlético by going 2-0 up through Afellay. It came courtesy of a lung-bursting run and cross from Domínguez; Mitroglou's ensuing dummy caused confusion between Diego Godin and Miranda, and the ball broke for Afellay to finish clinically.
However, with the interval looming, Mandžukić finally found the target, escaping his marker Éric Abidal to nod in Cristian Ansaldi’s precise centre and cut the arrears. Griezmann replaced Gabi in the second half for Atlético and the French international twice almost levelled for the Spanish champions, his first snapshot drawing a flying save from Olympiacos keeper Roberto and the second being tipped around the post.
Yet it was Olympiacos who got on the scoresheet next, with Mitroglou superbly controlling Pajtim Kasami's cross before swivelling to fire past Oblak. It was the Greece forward's first goal since netting for his country in the FIFA World Cup play-off against Romania last November. Griezmann then scored from Koke's superb cross but the hosts held firm.