Well, on a faster surface, at least, at Junior sublevel 8. After having read some very useful advice on how to use the slice (hadnt even found that key on my keyboard up until this match!) I used it consistently and patiently against Nadal in the final of Cincinnati where I defeated him by 2/6 6/3 3/6 7/5 6/2 in an extremely close match. The key was to force him to hit less topspin and when he hit it short I moved up and went for a forehand winner (my forehand profile were 80% power, 80% consistency and 100% precision). At times it seemed he was able to kick it up two gears, but he failed to do so towards the end of the final set.
So, my advice when playing Nadal and perhaps all excessive topspin players is to completely avoid the topspin. Instead slice all the time, or hit dropshots if you can do that successfully, and wait for a shorter ball, step in and hit a winner. Either way I think you´ll need at least one "killer" shot to finish the points. You´ll also need excellent speed and stamina. Mine were about 80 and 90, respectively. The serve seemed to be of lesser importance.
Some stats for my victory (me first): winners 109-84, errors 57-38, break pts conversion 42%-69%, total points won 148-144.