It is tough, but it is possible. ALthough the chance is not very large.
Australian Open: 70% chance. He is favourite here. Favourite surface, night matches and a pretty nice draw
French Open: 50% chance. Last year second, but with the long absence of Nadal now favourite. Murray and Federer are not that strong on clay.
Wimbledon: 30% chance. The thoughest one. Federer probably still largest favourite. And than maybe Murray also a bit larger favourite tha Nole here. But still possible.
US Open: 50% chance. along with Murray and Federer favourite to win here. If the conditions are on his side, good chance.
So a calculation: 70% x 50% x 30% x 50% = 6 % chance.
LMAO 6% chance. You sound like an actuary. Did Djoker have a 6% chance in 2011? You know what they say, there are lies, damn lies, and statistics.