Manchester United manager Louis van Gaal has been advised to make Netherlands and Aston Villa centre-back Ron Vlaar his third signing of the summer in order to add experience to the club's depleted defence.
Nemanja Vidic and Rio Ferdinand have both departed Old Trafford while Patrice Evra is also expected to exit the club, leaving a significant gap of experience in the United back four.
Vlaar stared for Netherlands during the World Cup under Van Gaal's guidance, helping the Dutch finish third in Brazil and McGrath says the Villa defender would be a valuable asset to United.
"Man United's defence is an area which could do with strengthening," he said. "Rio has gone and Vidia has gone as well.
"With Luke Shaw coming in, it's going to be a very young and inexperienced defence. I know they've got experience but there experience hasn't been good for them a lot of the time. They've played well individually. They're good players we all know that but playing together is a different thing.
"I'm hoping he'll bring in a good experienced defender and I think Rob Vlaar would be on that list."
Ander Herrera and Luke Shaw have joined United already this summer, but Van Gaal is likely to hold off making further additions until later this summer, having only officially begun his role at the club this week.
United leave for their pre-season tour of the United States on Friday and Van Gaal will assess his squad fully before deciding on additional signings.
"My method is always the same. I want to look at the players now, the present players," said the 62 year old. "Of course I know how the players play, but I don't know the players under my coaching. In the first three or four weeks I want to see what they can do. Then maybe I will buy other players.
"The players we have bought - Shaw and Herrera - they were already on the list. I gave my approval because I like them.
"First I want to see the players performing under my philosophy and how quickly they can pick up this philosophy. Now, I haven't worked with most of them so we have to wait and see. It's very important there's a 'click' between players and the manager."