Shawcross moved to Stoke on loan in 2007, before sealing a permanent move to the club in 2008, and after he was called up to the recent England squad, Pulis believes that the 25-year-old would not have been given the same chances at Old Trafford that he has enjoyed at the Britannia Stadium.
Pulis told the Daily Star: "He goes back to Old Trafford as an England squad man and captain of the club. I'm sure Sir Alex Ferguson is pleased as well that one of his players has come through and done so well.
"I'm not so sure Ryan would have played many games if you look at Vidic and Ferdinand.
"And I'm not sure Ryan would have made the progress at United that he's made here."
Shawcross has made 208 appearances for Stoke City.