Guendouzi will partner Granit Xhaka at the base of Arsenal's 4-2-3-1 and they will look to dominate the Sporting midfield. We'll have to wait for updates from Unai Emery after the game but let's pray it's not as serious as it seemed on TV.
Welbeck was rushed to hospital after the match and Emery reckons he has broken his ankle. But when you are playing football in competitive matches it can happen'. He's helped us with his behaviour, with his quality and his capacity. But I think the players were concentrated on the match and we forgot this injury the next minute on the pitch.
He added: "He's always encouraging me to be positive with the ball, always encouraging me to work hard off the ball for my team as well". But when the match finishes, the first thing they did was ask for him.
He will hope he did enough in that game to merit a spot at leading the line when Sporting arrive at the Emirates, on what is a big night for both teams. "We don't want it, but this is our profession".
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Supporters have taken to social media to say how "heartbreaking" it is while TV presenter and lifelong Arsenal fan Piers Morgan was among those to say how "gutted" they are for Welbeck.
The 27-year-old has overcome serious issues in the past, missing large chunks of his career with knee problems.
This latest setback comes on the day he was named in Gareth Southgate's latest England squad for the forthcoming games against the United States and Croatia.
A win for Emery's side against the Portuguese club will ensure Arsenal top the group.