Arsenal qualified for the last 32 of the Europa League after a match marred by forward Danny Welbeck suffering what appeared to be a serious ankle injury.
The Gunners were held to a goalless draw by Portuguese side Sporting Lisbon at Emirates Stadium to join Chelsea in the next phase.
Sporting ended the game with 10 men when ex-Barcelona defender Jeremy Mathieu was shown a straight red card after fouling Pierre-Emerick Aubameyang when he was clean through on goal – although the hosts could not find a winner.
But the fixture was overshadowed by the injury to England international Welbeck, who was carried off on a stretcher.
The 27-year-old was hurt in the 25th minute when he jumped for a header and landed badly on his right ankle.
He received oxygen and had his leg in a protective brace as he was taken off the pitch, with up to 10 medical staff around him as he received treatment.