One major problem for Nadal today, other than the obvious, and it's something he's struggled with his entire career, is his inability to end points with his down the line backhand. He either puts too much top spin on it, giving the opponent a chance to get back in the rally (and often times, reset it), or doesn't hit it close enough up the line, and it ends up almost landing close to the center (it's hard to describe but if you've noticed it you'll know what I'm talking about). So many times he had Monfils scrambling all over the court, stretched out wide to his right hand side, and Gael hits a short cross court forehand that Nadal is subsequently unable to put away, which unnecessarily extends the rally and often results in Nadal over-hitting and making the error out of frustration.
The other ground stroke related problem today is not pulling the trigger on his forehand up the line and especially, inside out early in the rally. Monfils will retrieve for days, and is really hard to hit through. The inside out forehand is the difference maker when you pull the trigger early in the rally and it's no surprise it's the shot Gael struggled to deal with the most when Nadal actually executed it. So many rallies could have been a lot shorter.
All in all, this can't be anything but a positive week though, in light of the past 18 months or more. But make no mistake about it, Novak isn't sweating this sort of performance. It's actually matches like this that tell me at this level, Nadal isn't taking a set off Novak. As in, Novak would probably have a harder time dealing with inferior players to Nadal.
And good god, that serve...