The Red Devils sold the England international to Arsenal for £16m on deadline day, but replaced him with a loan move for Radamel Falcao.
Owen feels that the trio of Falcao, Wayne Rooney and Robin van Persie are a potent threat, but believes that due to the trio's similar age, the club are leaving themselves short of options in the future.
He is quoted as saying by The Mirror: "Rooney, Van Persie and Falcao are a formidable trio. The only thing I would say regarding the sale of Welbeck, it leaves United with a very good attacking unit for the here and now.
"But after that – who knows? Welbeck at least has youth on his side."