Andy Roddick was made to fight hard in his semi-final against Thomas Johansson, going to a tie-break three times against the Swede.
Here Hawk-Eye commentator Jason Goodall explains how both players' different match tactics proved critical in the closely fought contest.
In the first set Johansson used his first serve very effectively, getting 60% in and varying things nicely in the advantage court. On the deuce court his tactics were more obvious; he was using the slice serve out wide in order to open up the court and then in the first groundstroke of the rally he was either going into the space created by the serve or back behind his opponent - the tactic worked very well.
Johansson won the vast majority of points on those slice serves out wide to the Roddick forehand so it was an excellent tactic to use.
Whereas in the second set Johansson's first-serve percentage dropped dramatically to 45%, which allowed Roddick a look at his weaker second serve. That is why Roddick was able to break serve twice in the second.
Roddick changed his tactics in the third set coming in to the net 23 times - and winning 17 of those 23 points. In the first set he only came in six times and in the second he only came in five times. So it was a distinct change of tactic in the third set and it worked very well.
In the fourth set Roddick improved his serve even more. He landed a healthy 70% of his first serves in and went on to win those points 87% of the time. When his second serve was in, he went on to win the point 100% of the time.
In all, Johansson won only three points on Roddick's serve in the whole of the fourth set.
So when things got tight for Roddick, he was still able to rely on his serve and that was the main difference in the match between the two men.
The American also did not serve a double fault - and has not done so in his last two matches - which, given he has such a powerful serve, is quite an achievemnet.