By Abhishek Mehrotra
However, it wasn't as straight-forward as it looked - especially in the final two sets, when Del Potro gave Djokovic a serious run for his money. Here are four reasons that go some way in explaining the final result.
The Del Potro serve and the Djokovic return
Del Potro served at 66 percent on the night, nine points higher than Djokovic. However, he won only 65 percent of the points when his first serve landed in. One of the reasons is the Argentinean's ball toss while serving. Unlike most other players who either toss it straight up or behind, Del Potro tosses the ball in front of him. This reduces the spin he can impart, but allows him to generate more speed, and at a greater depth.
At the same time though, it also means Del Potro is falling forward by the time he finishes his service motion, and needs one or two steps to steady himself before getting back into position behind the baseline.
Against most opponents, it wouldn't matter. But Djokovic is the best returner in the world, and he was getting a good read on Del Potro's serve on Thursday. This meant Del Potro barely had time to sort his feet out before the ball was speeding back over the net. This hurt him badly, especially in the first set when he was broken twice.
The Djokovic change of direction
Apart from being the best returner in the game, Djokovic is right at the top when it comes to changing the direction of his shots in an instant - from angled crosscourts to speeding down-the-lines. Most players are averse to doing it too often, for two main reasons.
Firstly, the ball needs to travel over the higher part of the net, which makes the down-the-line a risky shot to play. Secondly, when travelling straight, the ball needs to travel a lesser distance than it does when travelling crosscourt. It may not be a big difference, but the top guys play their shots extremely close to the baseline. Even small distances matter a lot.
Djokovic is able to achieve that precise blend of timing, precision and power consistently. On Thursday, he made the lanky Del Potro suffer by engaging him in crosscourt rallies before suddenly going down the line - especially off the backhand. Most players would have trouble with this, and Del Potro, because of his relatively poor movement, had even more so.
Del Potro's passivity
One of the keys going into the match was whether Del Potro would be able to control the points with his massive forehand.
He could not, or rather did not. For some reason, the 23-year-old chose to be conservative against Djokovic, electing to return in and around the centre of the court, again especially in the first set and paid a heavy price. When it comes to playing against the big three, opponents who play "first-strike" tennis i.e. those who take the offensive first are usually the ones who win. Tomas Berdych did that superbly against Roger Federer on Wednesday - grabbing the initiative and going for the lines from the beginning. Lukas Rosol did the same against Rafael Nadal at Wimbledon.
Except for a few stretches in the second and third sets, Del Potro was loathe to take too many risks, opting instead to play the ball back in safer areas of the court, allowing Djokovic to take control.
The Del Potro backhand
This is not specific to the match, but worth pointing out nonetheless. Because Del Potro is so tall (6'6), he needs to bend more than most players so as to hit up on the ball and get it to clear the net.
This becomes even more imperative if his opponent isn't hitting with a lot of topspin and Del Potro cannot take advantage of the bounce. Unfortunately, it doesn't come naturally to the Tower of Tandil - especially when he's getting tired.
This does not hurt him so much on the forehand - because he can still rotate his wrist to impart top-spin on the ball and get it to clear the net without having to crouch. However, because he has a two-handed backhand, his wrist doesn't have the same freedom on that stroke, and he has to generate the height on the ball by hitting up on it. That means bending.
Djokovic took full advantage, using the slice to keep the ball low. That saw Del Potro either slam the ball into the net or make a weak return which the world number two could use to take command of the point.