The Masters titles won by Borg in Jan. 1980 and Jan. 1981 could be added. That tourney was the 4th "biggest" during those years in my opinion, based on factors such as fan interest, prize money, and depth of draw. It was a BIG tournament played regularly before 10-20K folks at Madison Square Garden (about 19K for a Borg-McEnroe match in Jan. 1980). Players like Connors, Borg, McEnroe, Lendl, Gerulaitis, and Vilas squared off at the YEC and the AO was not even close to being as important and I would argue that neither was the WCT at that particular time (unlike earlier WCT finals that were a bit bigger). It was called the Volvo Grand Prix Masters at least in Jan. 1981 (see Borg vs. Lendl in the final below).