By Dan Marsh Erik ten Hag has made it clear that former Manchester United players are more than welcome to come back to the club after hanging up their boots. The Red Devils welcomed former striker Robin van Persie back to Carrington this week with the Dutchman observing training sessions as part of his attempts to gain a UEFA Pro coaching license. Van Persie, 40, spent three years at United after being signed by Sir Alex Ferguson back in 2012. Van Persie is far from the only former United player who has been in and around Old Trafford in recent years – and Ten Hag has now laid out a formal in…