I'm trying to think of anytime there was less than 2. There had to be several years there where Rafa and Roger were the only ones on the men's side what with Del Potro's injuries and before Andy, Stan and Cilic got on the board. Kuzzy has been there barring some injuries, since 2004. Ivanovic, Stosur, Kvitova have been pretty regular participants as well. Don't remember when all of them were out of a slam at the same time. Did Stosur, Kvitova and Kuzzy miss last year's Wimbledon or are you counting them?