Mario Ancic's retirement from tennis at 26 years old is desperately sad - he could have been a global star were it not for the mononucleosis that blighted the last five years of his short career.
Everyone remembers Ancic reaching the semi-final of Wimbledon in 2004 but the biggest match he played was two years before.
He took on Roger Federer in the first round at Wimbledon, right when everyone was beginning to get excited about the Swiss hotshot, but 18-year-old Ancic just put him to the sword. It was a quite phenomenal display.
He didn't get much further that year - he was knocked out in the second round - but by 2004 he was in the top 10 in the world.
Just before the recurring illness and injuries struck, he was up to number seven, and it looked like Ancic was the next best bet after Federer to win Wimbledon.
However, I think we all underestimated just how ill he was.
He worked so hard to come back, which makes his retirement so much more disappointing. I remember seeing him in Dusseldorf two years ago in the gym, desperately fighting to restore his fitness. It must have been exasperating for him.
He's made quite a bit of money in his short career, but he could've made a fortune.
If it wasn't for the illness, he could well have picked up a Wimbledon title - maybe other grand slam titles as well.
I'm certain he would've reached a Wimbledon final, in any case - he was that good on grass.
Ancic had a big game, built around a huge serve, and was fantastic at the net. He also moved really well for such a big man - he's 6'4" - but then he just lost too much weight.
He was quick and strong before his illness, but he lost that quickness as well as his strength, and it was really quite sad watching him battling so hard but failing to recover his previous form.
Ancic gave it so many shots, but as he said this week, enough is enough. He had other injuries to contend with - back problems, notably - but it was the mononucleosis that was the killer.
It's tough coming back from a big setback like that in tennis. There is support there, but it's not the same as the support you get from your team-mates in team sports. There's lots of good will, and I'm sure there were people looking out for him, but it's still incredibly hard.
He's a bright guy. I don't know him well - I've only met him a few times - but what I saw of him, I liked. He's one of those guys who seemed to have it all. He had the huge game, he was on his way to becoming a global star, and he's a good looking guy - the girls loved him!
He could've been marketed as a big, big star on the ATP tour. I definitely think he would've been knocking on the door of the big four - up there with Andy Murray and Novak Djokovic.
For me, Ancic was a better player than Andy Roddick, so if you look at everything that Roddick has managed to do over the past few years - he was number one in the world, remember - then I think a fit Mario Ancic would have at least matched those achievements.