The 23-year-old striker swapped Old Trafford for the Emirates Stadium in a £16 million move on Deadline Day and has since impressed on the international stage, scoring twice for England at Switzerland on Monday.
But Venables thinks United should be 'cursing' at the moment and, by contrast, can imagine a big smile on Arsene Wenger's face.
"I bet Manchester United are cursing right now. One thing’s for sure, their loss is Arsenal’s gain as Danny Welbeck proved with two superbly-executed goals," Venables wrote in the London Evening Standard.
"The irony is that United waited years for Welbeck to blossom and then decided to get rid just when he’s ready to reward them for all their patience. It was a bloody bad decision on their behalf. I can just imagine the smile on Arsene Wenger’s face right now."
Interestingly, former Manchester United captain Bryan Robson agrees with the 71-year-old.
In fact, Robson says selling Welbeck is the one thing he wouldn't have done at United this summer.
"At the last minute, Danny went to Arsenal and I thought ‘that’s the one move I wouldn’t have done’," Robson is quoted as saying by the Daily Mirror.
“But I tell you what it is - it’s a great signing by Arsenal and I’m sure Danny will do a really good job for them. United have added some real quality players to the squad but I would like to have still seen Danny as a United player.”