It's the question that's been on the lips of the tennis world since Baghdatis came from two sets down against David Nalbandian on Thursday to win that remarkable five-set semi-final. My answer starts with, but by no means ends with, two words: big balls.
The kid himself said he had no idea how he managed to get back into it against Nalbandian but the fact is, he did. His attitude is great. Mentally he hasn't let big-name opponents or adverse situations unsettle him, including the odd bad line call, especially a big one at a vital time in the semi. He's taken on, and beaten, four seeds, three of them top-10 players: Andy Roddick, Ivan Ljubicic and then Nalbandian.
Physically he looks strong. Sure, he's puffing at the end of some hard points, and appears to be ailing towards the end of long matches, but his weariness vanishes like morning mist as soon as he's up off his seat again.
His second serve needs some work, but there's not a lot of significant weaknesses in his game. And his strengths have outweighed his frailties in the past fortnight. He's been steady as a rock, Mr Cool, playing his game, and picking off opponents by targeting individual weaknesses in them. Against Nalbandian, for example, he hit the long serve, into the body, knowing Nalbandian is uncomfortable with that height. Against Roddick, the big hitter, he really mixed it up.
And, of course, he's had the rousing support of all of Melbourne's Greek community. No one should underestimate the power of the buzz that an atmosphere like that can give you. Baghdatis will feel like a king right now. He's already been offered yachts and goodness knows what else. If he stood for election he'd be prime minister in a flash. He's not just doing this for himself, but he also has absolutely zilch to lose.
So how did he reach this final, and why now? Unknown, underrated, and an underdog. Each of those played a part. Yes, we know he was a good junior, the best in 2003, when he won the junior Australian Open. Yes, we knew he'd been climbing the rankings, to No 54, because he's starting to mature, and become more consistent - a key ingredient in Slam success.
But he's still a novelty for most Tour players. And no one could know that this would be the event where he took his consistency to a new level. His more audacious shots work more often because he's realising exactly when they'll work best, and as importantly, when not.
The magic of sport is its unpredictability, major breakthroughs included. This may or may not be that leap for Baghdatis. I wouldn't make such judgements on one event. But he's earned huge respect, itself another asset for the future.
Federer will need to put him in his place quickly tomorrow, and I believe he will, and win. Federer has all the variety, the cool, the sheer consistency of pure talent that Baghdatis's other opponents did not. Some say Federer has underperformed. I guess by that they mean that every single set in every match has not been jaw-droppingly perfect. I prefer to interpret his "underperforming" as being able to shift through the gears just when he likes, especially when in danger.
I'd settle for underperforming like that! Baghdatis would, too. It could be quite a spectacle.