Young completed a £17 million move to Manchester United in June, before former Middlesbrough star Downing left for Liverpool in a deal reported to be worth as much as £20 million.
And Bent, who arrived at Villa Park in an £18 million move from Sunderland in January, believes the club have lost two of the best wide players in the Premier League.
"It's a big loss to us, you can't dispute that," Bent said in the Daily Mail.
"Ashley in particular was here for a long time - they are going to be a big miss, so you can't hide from that fact.
"Any striker needs good service at the end of the day, and Stewy and Ash give you probably the best service in the division."
But despite his disappointment at the departure of his England colleagues, Bent fully understands why the pair left Villa Park.
"What they did was for their careers – Manchester United and Liverpool are two of the biggest clubs in the world, so they've got their reasons for doing it.
"In fairness, I was in Ash's ear everyday, texting him. When we were away with England I was on his case all the time. I kept texting him: "One more year," for weeks and weeks.
"But at the same time, I fully understand. It's Manchester United at the end of the day – the biggest team in the world, so I wished him good luck and hope he does really well."
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