OTTH, Borg won the FO (when 1st) and Wimbledon in '78 & 80, but only got to the final of the USO! Nadal might have had a chance in '10 winning 3 in a row, except AO 1st in the season and he had to retire in the 3rd set in QF to Murray due to injury!
Of all the 3/4 Slam winners, Rafa is the only one to have won RG, Wimbledon and US in same year. 2010.
Looks like Rafa is the one that has come closest to CYGS in 2010. Would have won if not for AO injury.
THREE-QUARTER SLAMS
Male Open Era players who have won three Grand Slam events in a season:
1974 Jimmy Connors, United States (Australian, Wimbledon, U.S.)
1988 Mats Wilander, Sweden (Australian, French, U.S.)
2004 Roger Federer, Switzerland (Australian, Wimbledon, U.S.)
2006 Roger Federer, Switzerland (Australian, Wimbledon, U.S.)
2007 Roger Federer, Switzerland (Australian, Wimbledon, U.S.)
2010 Rafael Nadal, Spain (French, Wimbledon, U.S.)
2011 Novak Djokovic, Serbia (Australian Open, Wimbledon, US Open)
2015 Novak Djokovic, Serbia (Australian Open, Wimbledon, US Open)
https://www.usopen.org/en_US/search/index.html