Problem for Chang was that there was always a dominant player on every surface, and he was never quite it. He was always right up there with the contenders, but deep down everyone all knew that if just one "top" player got hot during the course of a slam when playing him, he'd probably lose. If a top player was a little off his game or just playing average, Chang would probably win; but honestly there's a reason why Agassi said that of all the top ten players he preferred to play Chang the most. He said that although Chang was great he felt that of all the top ten players if he was playing well, Chang made it the easiest for him to play his game. Why is that? Quite simply because Chang's average shot simply wasn't forcing enough, it kind of just sat there begging to be creamed, not too slow, not too fast, not too much spin, not too little, not too short, not too deep, etc. Basically it was like playing a ball machine set up to feed you balls just where you like 'em. The trajectory of his shots, neither super high or super flat, were adaptable to pretty much every top ten player's ideal strike zone regardless of whether they used an extreme western grip or an old school eastern. The truth is that he really didn't have any weapons other than his speed and nifty little, angled backhand passing shots/returns to outright hurt you with, and because Agassi didn't volley much that wasn't a factor.
Nadal's not like that as you saw when he played Agassi recently. A fired up Nadal's balls JUMP, which induced many errors from Agassi as the ball bounded just out of his strike zone at the last second. You saw the same thing against Federer in Miami earlier this year. Also, Nadal unlike Chang has the potential to hit for pure pace when he wants to AND actually still keep it in, unlike Chang who whenever he tried to smack one would more likely smack the back fence. Nadal's also a lefty, and his shots have FAR more work on them than Chang's. Chang's shot just sat there. Nadal's shots at their best make your racket twist in your hand and induce errors because of their action. Nadal can win baseline points by forcing errors as well as just retreiving until you miss. Chang could only hope that you missed if another top player was having a good day.
I think the more apt comparison is a PEAK Thomas Muster. In spite of what people say about Muster not being able to play on faster stuff, he was the second best player behind only Sampras in the first half hardcourt season in 97 when he decided to focus on hard courts. Muster's peak was very short lived, but during that peak he burned intensely. I think he got unlucky in 96 as the French played abnormally fast that year. Had the conditions been normal, I think he would have won the whole thing for sure. He had a three year window, where he was a force. He did not focus on hard courts for two of those three years, because his knee couldn't take the pounding for obvious reasons for extended periods of time. In 97 he made a concerted effort at the beginning of the year though to prove he could play on hardcourts and he did. The only player with a better record was Sampras who had his best start record wise to a year ever that year.
To me, PEAK level Muster is much more similar comparison to Nadal. Both are lefties with average serves but HUGE, HUGE, HUGE hearts that cannot EVER be counted out in a match. Unlike Chang, however, they also had power and WEIGHT behind their shots, crazy, HEAVY spin that induces errors all by itself...unlike Chang who needed you to miss, he couldn't force you to miss. Muster and Nadal are both JOCKS, exceptional athletes, muscle bound, strong like ox yet so light on their feet and with a mental altertness to the ball that allows them to retrieve virtually any ball they set their mind to retrieve...which is pretty much every ball. Both players, however, are vulnerable against guys with big serves who can swing them out waaay wide and knock away the volley to the open court. Why? Because they both choose to stand way too far back in order to get a full cut in. This means that if an attacking player is hot under fast conditions, they're definitely vulnerable. Still, this does not mean they're not formidable.
I'd say that Muster would have won the 97 Australian for sure had he not had the misfortune of running into a red hot Sampras. Had he kept up the early pace he showed in 97 on hard, I think he could have well won more slams.
Muster's a unique example though. His knee really set him back, and it took him a looong time to hit his peak. And when he finally did, it was relatively short lived. It was not ended by injury either, it was basically ended by him burning out. He said after winning the 97 Lipton that it was sweet justice. He played AMAZING that tournament, certainly good enough to win a hard court slam, BUT you could see in his eyes that he laid it ALL on the line to win that tournament to get back at his personal demons for screwing him there so many years ago. After that, he was never the same. Check his results immediately after that. He was a total dud. Quite frankly, he stunk. He played a very tight match with Kuerten at the French, but other than that he really did stink. Mark Goellner nearly knocked him out in the first there, Rafter knocked him out on clay in his hometown, he lost early at every clay tournament leading up basically. He just totally lost it after that for some reason. Then against Henman at the US Open later that year? That one point where he jokingly chased Henman? That was NOT like Muster. The ferocious bark in him was gone, he just didn't have the same intensity anymore, and it suddenly made him look very normal.
It used to be that the LAST person on earth you'd suspect of sudden burnout would be Muster, because he of all people seemed to be consumed by such FIRE when he played. Yet, the ironic thing is, that Muster is the one who let himself the most go and flamed out the most precipitously. The next year, he got worked by pretty much everyone, and I don't even think he really cared anymore. He shortly unofficially retired thereafter and lost ALL interest in the game completely for years until his doctor told he better start getting in shape again because he had gained fifty pounds. That to me is just amazing...but it happened.
Not saying this could happen to Nadal. But like everything else in life, it's a possibility. Nadal is just soooo fired up out there allllll the time, that one wonders if one day he'll fall in love or something with a girl or who knows what else and suddenly tennis won't seem that important anymore. In all honesty, tennis really is just a game. It's NOT that important. Michael Stich understood this fundamental truth, Andrei Medvedev did too. That's why guys like that fall short of expectations. But whose expectations are we talking about? There's or their handlers who have vested interests? Medvedev said it best when he said the other players schedule their lives around their tennis, but he was more the type who scheduled tennis around his life.
What makes guys like Muster and Nadal at PEAK intensity so great is that they simply want "it," whatever that means, more than you. I think it's always intimidating to play someone you know wants it more than you. When a guy seems to be playing every match like it's his life on the line, that's awe inspiring and generates fear in other players. But really as long we're all human here, EVERYONE has an epiphany sooner or later. One day, Nadal will wake up and realize that hey, he just doesn't feel like training anymore. Just doesn't see the point. Muster of all people did. Heck, even Lendl's put on the poundage. Then again, McEnroe's fire's still burning strong. Everyone's different. Sometimes you just wake up and tennis no longer seems that important. You gain perspective and realize it IS just a GAME. What we imbue upon a game is what we imbue. We can paint baseball as the most beautiful game and think of Field of Dreams and The Natural, and we can also just wake up one day and realize we want to flip the channel in the bottom of the fourth, either that or fast forward to the bottom of the ninth. At a certain point, the process becomes mundane, and at that point, when players just want to fast forward to the good stuff, the pivotal moment, the glory, the championship match, etc. to get excited, that is when you know it is time to pack it in.
For me, I'd say the question is not whether Nadal has the capacity to go down as an all-time great type player, because to me he clearly does. But the REAL question is can he maintain his peak level of interest, this level of consummation by the sport, for how long? Had Muster's knee not been surgically reconstructed and he been able to play on hard courts more, I think he showed in early 97 that peak Muster could win on any surface. Give him a peak 95 - first half of 97 without the bum knee and extend that for an entire career, and you have yourself the makings of an all-time great caliber player whether you want to admit it or not. The problem with Muster's legacy is that he started to build it too late in his career, and when he did begin to build it; he just as soon flamed out.