The 23-year-old signed a long-term contact with the Gunners on Monday after the striker was deemed surplus to requirements at Old Trafford.
Welbeck scored nine goals in 25 Premier League appearances last season, leaving Old Trafford having scored 29 goals in 142 games in all competitions since making his debut in 2009.
The forward, who will wear the number 23 shirt for Arsenal, won the Premier League and League Cup during a six-year spell in the United first-team.
Welbeck is currently on international duty and England boss Roy Hodgson revealed that he had picked up a knock in training on Tuesday.
“Unfortunately in training today he received a knock in the session,” said Hodgson ahead of Wednesday’s clash with Norway.
“I would be very disappointed if he could not play because of what happened with the last kick of the session.”
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