Everyone has "what if" moments. What if I'd done better at school. What if I'd been more charming with that girl instead of vomiting in my mouth when I tried to talk.
But for David Moyes it's a bit more serious than that. He would be forgiven for having full-on Sliding Doors flashbacks.
Not only has Louis van Gaal, Moyes' replacement as manager of Manchester United, been handed a more comfortable start to his first season at Old Trafford, but he's also managed to sign two of Moyes' targets without even setting foot in the manager's office at Carrington.
United have signed Ander Herrera and Luke Shaw for Van Gaal, with the promise of more to come. Moyes was left scratching around on deadline day and ended up paying more than he should have for Marouane Fellaini.
But it's not just luck and circumstance that separate the two. The World Cup is evidence of that, if any were needed.
Just as United fans will be looking forward to seeing Shaw and Herrera, they will have been excited to see just what kind of manager they have appointed.
Once the players walk out onto the pitch, there is very little a manager can do. Managers don't score goals or miss chances. They're not responsible for defensive mistakes or flashes of creative genus.
But the best managers, the ones who come out on top more often than not, find a way to influence big games, even if it is only from the touchline.
It's something Moyes didn't to do enough in his eight months at Old Trafford. His record against the top four clubs was proof of that.
Van Gaal, meanwhile, has seen his Netherlands team go behind three times at the World Cup in Brazil. But each time they've found a way to win, and now they're in the quarter-finals.
Van Gaal lost his key midfielder, Roma's Kevin Strootman, before the tournament began, but the 62-year-old has shown himself to be tactically flexible, preferring 5-3-2 over 4-3-3 because it better suited the players he has available.
It's the fine margins that count for a lot at the highest level.
United have already spent more than £60 million during this transfer window. With the squad still short of a centre-half and another midfielder, they are unlikely to stop there.
But amid all the excitement of "war chests" and "come-and-get-me pleas," United might have already made their most significant signing.
And he won't kick one ball next season.