It's been terrific, the way Juan Martin del Potro has come back from his nine-month injury lay-off and, for me, something of a surprise.
Some players are simply never the same after suffering such a severe wrist injury - the joint's not as strong as it was, and the time it takes to recover can really take its toll.
It also wears on the ambition of a player and, lest we forget, Del Potro is already a multimillionaire with a Grand Slam title to his credit.
Despite all these possible set-backs, however, it looks like the 22-year-old is as hungry as ever!
His rise this season has been impressive; reaching the semi-finals of Indian Wells and beating Robin Soderling in Miami - which was a huge result for him.
Things are looking good for the Del Potro at the moment. His ranking is up to 46, and I think that very soon he's going to be in the top 32 - which will mean he gets seeded for Slams.
Once he's in that position he'll be a heck of a prospect to reckon with on any surface.
Before his injury, the Argentine showed how dangerous he can be on clay.
He reached the French Open semi-finals in 2009 (losing to eventual champion Roger Federer), and he was in the top four in the world as recently as January last year.
He has so much power, and a pitbull-like attitude to competition.
Add to that the fact that he moves particularly well for such a big man (he's 6'6"), and it's not inconceivable that he could develop into a big, big threat this year.
His style isn't always particularly pleasing on the eye, and sometimes it's easy to underestimate the qualities of players like that - you don't get too many 'ooh's and 'aah's when Del Potro plays.
The shear power of his serve - and particularly his ferocious forehand - just breaks people down.
The one thing that concerns me about Del Potro's comeback, however, is that tennis has moved on since he was last at his peak.
Rafael Nadal is a better player now, and - despite going through a bit of a dip - the same can be said of Federer. As for Novak Djokovic, well, the Serb is considerably better than he was a year ago.
For that reason, I don't think that Del Potro will be able to break into the upper-echelons of the men's game - the top three.
I definitely see him getting back into the top 10, and possibly the top five, but after that I'm not so sure.
If he does get back to fourth, it will be a fantastic achievement in itself.
I'll certainly be looking out for him tomorrow, when he plays Soderling again in the Estoril Open quarter-finals.
The Swede is such a good clay-court player that a win for Del Potro would mean an awful lot, and it might just be a sign that he's going to go deep into Roland Garros.
I've said before that Nadal - despite failing to reach his peak on clay yet this season - is virtually untouchable on his favourite surface.
However, if Del Potro's graph continues to rise the way it has been doing so far this season, I can certainly see him as a possible threat to the Spaniard's clay-court dominance.
Rafa will see certainly be seeing him as a real threat, of that I'm sure.