Following the match, which ended 0-0, Arsenal manager Unai Emery confirmed Welbeck had been taken to hospital for further treatment.
Welbeck landed awkwardly after attempting to meet Stephan Lichtsteiner’s cross in the 25th minute and immediately began to writhe around in pain.
The 27-year-old striker was given oxygen on the field before being stretchered off with his right leg in a brace, as players from both sides watched on in distress.
“Danny looked like a serious injury, which is not good to see, so our thoughts are with him,” Arsenal goalkeeper Petr Cech told BT Sport.
Welbeck’s former Manchester United team-mate Nani was one of the first players on the scene and attempted to comfort a player he spent seven years with at Old Trafford.
Arsenal midfielder Mesut Ozil, who was not included in the squad to face Sporting, tweeted during the match to wish his team-mate well.
“Oh no… get well soon Danny,” Ozil wrote.
With some of the game’s intensity lost following the serious injury, neither side were able to break through as Arsenal secured the point they needed to qualify for the next round.
The England forward’s career has been blighted by knee injuries, but he appeared to have overcome them and was a part of Gareth Southgate’s squad at the 2018 World Cup in Russia.
Earlier on Thursday, Welbeck had been named in Southgate’s latest squad for an upcoming friendly with the USA and Nations League encounter with Croatia.