Luke Shaw is a dream for headline writers.
"Luke's Shaw to be a hit at Manchester United." "Reds have signed a Shaw thing." They write themselves.
But in reality, nothing is certain. You can watch a player again and again. You can check up on everything from his fitness record to his personality. You can find out what he has for breakfast if you want to.
But signing a player is always a gamble. Andriy Shevchenko averaged better than a goal every two games at Milan but couldn't hit a barn door at Chelsea.
Likewise for Fernando Torres, who even had experience in the Premier League under his belt before he moved to Stamford Bridge. Price, reputation...none of it matters. Some moves just don't work out.
But if ever there was a time for United to gamble on Shaw, it's now.
United need a left-back. They like to buy British. And they like to buy young. Tick, tick and tick.
Even if Patrice Evra isn't lured back to France at the end of his contract this summer, he's 32 years old and will need to replaced sooner rather than later.
This past season, Shaw proved himself as one of the best full-backs in the Premier League. Still only 18 years old, he's got plenty of time to get better. And he's English.
Born in Surrey and part of Southampton's academy since he was a schoolboy, only he will know if he can cope with a move north, away from family and friends.
But United's transition offers the perfect opportunity for new arrivals to settle.
Shaw has never played in the Champions League before. And he won't next season if he decides to move to Old Trafford.
And even if they finish in the top four at the earliest available opportunity, Shaw will have a year of experience, a year with his new team-mates, already in the bank.
Young, English and talented, he won't come cheap if he chooses to leave Southampton. But United have been caught out before.
Michael Carrick joined Tottenham for £3.5 million in 2004 before United paid £18.6 million two years later.
Rio Ferdinand signed for Leeds for £18 million in 2000, but his price had nearly doubled by the time he moved to Old Trafford in 2002.
If Shaw is worth the £27 million that Manchester Evening News' James Robson claims he is after 64 Premier League appearances and before his first World Cup, what might he cost after he comes back from Brazil? Or in two years' time?
It will be a gamble for United to sign Shaw this summer. But that's true of any player. You can never be certain it's going to end in success. Just ask Shevchenko. Or Torres.
But it can be just as big a risk to pass up the opportunity when it comes along.
Shaw won't be available indefinitely. And there's always someone else willing to take the punt.