I believe LVG sold/released around 25-30 players as well during this time. That worked out well.
He gets a lot of stick for it, but moving on a lot of those players was the right thing to do.
Lindegaard - No complaints
Amos - No complaints
Büttner - No arguments there
Rio - He retired a year later after a difficult season at QPR
Vidić - Struggled with injuries and basically retired after 1 poor season at Inter
Evra - He could maybe have stayed on as a squad player. The club had just signed Shaw.
M.Keane - He went on to have a decent career, but wasn't United standard
Rafael - Loved him and thought he would go on to become a top RB under SAF. But based on his career post United, we didn't miss out on much.
Evans - He's one of the main errors people mention. He was so bad during LvG's 1st season, I can understand why he was sold. He did rebuild his career at WBA and earn a move to Leicester where he won an FA Cup.
Kagawa - He just wasn't cut out for The PL. Apart from a good 15/16 season back at BVB, he never really found the form he showed prior to United.
Fletcher - Having been troubled by colitis and injuries, this was for the best. He was able to find some joy at WBA.
Anderson - A fan favourite in some ways, but it was time for him to move on
Zaha - This is one we should have handled better. Between Moyes and LvG. He might not have made the cut, but never really got the opportunity to develop.
Cleverley - No complaints, he didn't go on to do much after leaving.
Nani - I really liked Nani between 2009-2012, but he became injury prone by the time SAF announced his retirement.
Di María - Such a shame that this didn't work out. It does seem that his heart was never set on the move though
Welbeck - I was gutted at the time. In hindsight, it wasn't a bad fee for a player who would be plagued by injuries after leaving
Henríquez - Never went on to do much after a prolific loan spell in Croatia
Chicharito - Another fan favourite. He was very good for Leverkusen. We could maybe have found a squad player role for him.
van Persie - We could probably have held onto him for 1 more season, even if he wasn't the same player as during the 12/13 season.
The bolded are the only real what if or what could have been scenarios for me. The problem, as it is now, is that the players that replaced them were questionable.