Arsene Wenger has confirmed that Welbeck will be out until next month's international break with a groin injury he picked up in the 0-0 stalemate with Chelsea this Sunday.
Welbeck will miss Wednesday's Carnao Cup clash with Doncaster, Premier League games against West Brom and Brighton and a Europa League tie at Belarusian side Bate Borisov
Wenger told the club's official website on Tuesday: "Danny has a scan today. We don't know how bad his groin injury is but he will certainly be out until the international break."
Arsenal's first game after the international break is an away game at Watford on October 14.
Mesut Ozil remains sidelined with the knee problem which kept him out for the trip to Chelsea and Francis Coquelin and Mathieu Debuchy will also be absent on Wednesday.
Wenger said: "Mesut is training again, but for (Wednesday), no (he will not feature). He has a little inflammation of his knee."
On the team he will select for the game against Doncaster, the French coach said: "It will be a similar team to the one that played against Cologne," and he confirmed that Jack Wilshere and Calum Chambers would both feature.
Goalkeeper David Ospina, club captain Per Mertesacker, Mohamed Elneny, Ainsley Maitland-Niles, Theo Walcott, Alexis Sanchez and Olivier Giroud all started in the Europa League tie last Thursday before being dropped out of the starting XI for Sunday's draw at Stamford Bridge.
In the clash against Doncaster, Wenger will hope to build on the morale-boosting point and performance against Chelsea, at a ground where Arsenal had lost their five previous visits, and he will want to carry the momentum into the West Brom contest on the weekend.