he's carrying some extra pounds
im 5'11 160, and i think that probably perfect height to weight ratio
extra weight slows you down, even if its all muscle- slows you down, he needs to tone more
IMO 5'11" 160 lbs is a bit lanky even for a tennis player. Rafa and Blake both have good builds for a tennis player. They're also two of the fastest guys in the ATP. Rafa isn't carrying that much mass, either, since he really only has a muscular left arm and not much bulk anywhere else.
From ATP's site
Nadal - 6'1" 188 lbs
Blake - 6'1" 183 lbs
Subtracting 6 lbs for each 1" above 5'11" (that's the average that each inch increases in weight), you have 5'11" 176 lbs and 5'11" 171 lbs. I'd say that 170-175 is more around the ideal weight for that height (at least for a tennis player).
But you can't really make a perfect height to weight ratio, since that depends so much on bone structure and whatnot. Some people have broad shoulder girdles, large joints, etc. which can really increase weight.