The SPFL Premiership side accepted an improved £600,000 offer for the 17-year-old from the Barclays Premier League club earlier this week, with the Angus teenager travelling south to look around the club's facilities, but McNamara is not convinced that the move is right for the centre-back.
His argument is that Souttar would benefit more from playing first-team football at United than he would from being involved in an academy side in England. McNamara said: "There have been bids for John but he's still our player. Nothing has changed. He's spoken to them and been down there but my advice would be to stay here and play football.
"We're not standing in the way of any player who wants to further their career. But I've told him we're here to help. He's playing in the first team and he's only 17. It's all about seeing what the best for of progression is for him, like staying here and playing 150-200 games for the first-team."
Far from being troubled by reports linking Souttar and fellow teenage talent Ryan Gauld with moves from United, McNamara believes that it can only serve the club well. Indeed, he would have no qualms about selecting the defender for tomorrow's game with Kilmarnock because he is unlikely to be adversely affected. "He's a level-headed kid," he said. "And it's great that there is that level of interest in him, along with Ryan. They're developing and it shows that Stevie Campbell and the rest of the youth staff are doing a fantastic job. As the manager, I get the benefits.
"I think John should stay. But it's been important to have had that dialogue with him rather than just turn things down point-blank. We'll give him all the encouragement he needs. I think he's excited at what is happening. He has other options as well like speaking to his parents. But he is in my first-team squad and is involved each week. What is the best for of progression for him? Is it to stay and play regularly in the first-team or go down there and go into the youth academy, which looks the most likely scenario at this moment?"
Should Souttar depart, it may well enable United to move for Morgaro Gomis, who has been training with the club after leaving Birmingham City. "It would be good to bring him in but the problem is the timing," said McNamara. "We've used our budget but hopefully something can be done. We'll see what happens."