A good loan can be the making of a player, as Jonny Evans, Danny Welbeck and supporters from the Stadium of Light to Old Trafford can attest.
The United duo each spent a year with Sunderland, aged 19, and can thank Saturday's opponents for providing the schooling during a key period in their burgeoning careers.
Evans spent two six-month stints with the Black Cats under Roy Keane, initially joining for the latter half of the Wearsiders’ 2006/07 breathless promotion push and then repeating the feat a year later in the top flight. Welbeck spent the entire 2010/11 campaign under Steve Bruce.
Since returning to Old Trafford, the youngsters have established themselves as fixtures in Sir Alex Ferguson's senior squad, utilising all the experiences and battle scars of their time with Sunderland.
"The environment that Sir Alex Ferguson sent Jonny and Danny into with the people who were at Sunderland was a perfect type of nesting ground for them to flourish," says ex-United defender Michael Clegg, now strength and conditioning coach at the Stadium of Light.
"I can put my hand on my heart and say that Jonny gave everybody that bit of confidence we needed at the time,” recalls Clegg. “The team kicked on and I'd say he could have been captain just for what he brought to the place. We had a run of around 20 games where we lost just once and Jonny was a massive part of that.
"As a young lad coming into a situation which was new to him, he stood out a mile as somebody who could kick on to bigger and better things. I think it helped at the time that Danny Simpson was there with him and he had somebody to bounce off and bond with. He did really, really well and the season went from bad to good to great. The team had great work ethic. They worked hard, got stuck in and there was a great bond between the lads and it culminated in us getting promoted.”