As I have observed in yesterday's live commentary thread, Nadal started serving better when he was down by a set.This was supposed to be reserved for the final against Djokovic but he pulled it out yesterday. His fastest serve was up to 197kmh, just a little bit slower than the other two taller guys(204kmh for Murray and 201kmh for Djokovic respectively).
His average first serve and second serve speed were even faster than the tall Murray (174kmh vs 173kmh; 139kmh vs 133kmh) and he is only a bit slower than Djokovic who has 180kmh for first serve and 146kmh for second serve)
Bear in mind Nadal's serve is not known for the speed but the spin, especially on clay. His serve kicks high and has heavy slice. Spin and slice makes the ball a bit slower. So a 170kmh+ first serve from Nadal can be as good as a 190kmh+ first serve.
The king of clay is back. I am sure his service performance will further improve in the final.
Poor form argument again not working since Nadal always reserves his best for grand slam? Djokovic's chance is getting slimmer and slimmer.
Additional stats on Nadal's serve:
2013USO F:1st serve average: 176kmh, 2nd serve average 141kmh
2013RG SF: 1st serve average: 179kmh, 2nd serve average 143kmh