No question his absence created opportunity and I don't think it's a coincidence that the veterans are the ones who took advantage of it. The guys who have been around a bit and seen the Rafa-Roger dominance and with him out of the event it had to serve as motivation.
Cahill told the anecdote about the pain from his tendinitis being so bad (despite daily icing for nearly 3 years) that he was actually in tears from the pain one day boarding a plane. Hope that his case is not as severe but from what I'm told by a couple of specialists: rest is the best remedy. I would think he's really got to consider cutting down the length of his practice time or doing more off court training. Patrick McEnroe told the story about Nadal practing 4-5 hours a day the week leading up to last September's Davis Cup semifinal. I would think he's got to cut that down just to reduce the strain on his knees.
I've never had knee problems, but a few friends who played college sports have and I know one guy who was a college basketball player with chronic tendinitis (he's been out of college about 15 years now) who can't even really run without pain - and this is from 4 years playing college ball, not 7 + years at the pro level. Did you read the NY Times Magazine piece on Nadal a couple of weeks ago?
A few comments in there from Nadal's doctor, Angel Ruiz-Cotorro, and from Uncle Toni really stood out. When Ruiz-Cotorro said "more speed, bigger problems..." (alluding to the speed of the game and the speed with which Nadal plays) and when he said: "For an athlete like this, the word 'rest' does not exist...."
Asked Courier about his own experiences (he never had knee problems, but had the dead arm issue) and he said in retrospect he feels he would have been better off cutting back on his own training or at least reducing the length/intensity but when you get to No. 1 through such hard work there's a tendency to try to work even harder when things are not going as well which can be counter-productive in the long run.
The other interesting point was Uncle Toni was talking about Nadal's serve and acknowleding the fact that he's a righty playing lefty does inhibit his serve: "It's possible he'd be serving better if he played right-handed. Throwing the ball perfectly is hard for him and he doesn't always hit it at the correct height. The whole thing is just not something he does very well. We're working on it," Uncle Toni told the Times.
His serve is definitely much improved from his early days and to me if he can develop that more extreme lefty slice out wide on the ad side that could make his life a lot easier by helping him shorten up the points. Uncle Toni's comments kind of echo what McEnroe has said for a long time that maybe because he isn't a natural lefty he can never fully develop that biting slice wide that McEnroe had that even guys like Korda, Leconte, Forget, etc. could exploit. If the tendinitis is going to be a long-term issue then hope he can pick up his serve even more to shorten points. Seems like if he can do that and manage his schedule and training time would be beneficial.
The good news is he probably will only play 2 hard-court events before the Open so assuming he does come back for Montreal then he'll have had more than 2 months of rest. Then the question is how do the knees hold up playing Montreal, Cincy, US Open in succession?