As I'm sure most of you have notice since Toronto Roger has a new style of serving the first ball. He mixes up fast flat serves with what looks like classic 2nd serves ( more topsin or slice rather than power). Thus you see him nowadays serving the 2nd serve faster than the first.
To see the reason for this change I think we must go back to what he said after his RG defeat aginst Soderling:
Originally Posted by Federer
Because, I mean, these were some serious, tough conditions, you know. If you serve 225, 230, you can still hit through the court on the serve.
I may be lacking those 5 to 10ks extra on the serve to hit through a guy on the serve, but that's the way conditions are. I can't complain, because it was the same for both of us.
After RG I saw Roger hitting some very fast serves in Halle. Up to 220. But after Wimbledon he said he had some minor back problems. Could it be that those extra 5 to 10 ks were the ones that trgigered them ? Pretty likely.
So what I think might have happened was Roger realizing that he was hurting himself trying to go for more power and decided to change his new approach by 180 degrees .
Today we see that the top players stay 2-3 m behind the baseline from where they can eassily return a 200+kph serve (the most obvious case being Nadal).But dosen't those 2-3 m behind the baseline make them vulerable if they have to return a slow slice serve insted of the big flat serve ? Hell YEAH!
If you can mix flat serves with 100 mph kickers I'm sure that even the best returnes in the game Nadal, Murray, Nalbandain will have major issues.
Of course today Roger's serve is at it's most vulnerable point in the last 7 years because of the changes but I think this new dimension of the serve could be the future.