Cincy is not as important as the World Tour Finals (both of which Nadal's best showings are two semi-finals). WTF is definitely the biggest event Nadal hasn't won yet.
I would say it is the only
big event he hasn't won. Cincinnati, Paris and Miami don't really matter in my book. The WTF is the only thing lacking in his resume.
I am actually quite alarmed by the number of times in the last two days where I've seen people on here and in the press say that Nadal has now won every important title in tennis.
Have they forgot about the WTF? They always remember to mention the Olympics which has little history but the WTF is barely ever mentioned. It is mind-boggling for me. I guess I'm in the minority that rate the WTF highly.
Nadal will probably win the WTF some day and when he does he has every title that matters.