Let us look at the remaining slam winners' paths in the draw - Murray, Wawrinka, Nadal, Federer.
Even though they are aging, I believe they still have an advantage over the field until someone else finally breaks through.
At this point, based on the draw in the bottom half, one would have to like Rafa's chances. First, he is the only slam winner in the bottom half. This is a big advantage, no? His arch-nemesis Djokovic is gone, leaving him what appears to be a relatively easy run to the final if he can play somewhere near his best. In the 3rd round he has young, still inexperienced #24 seed A. Zverev (Rafa leads H2H 1-0). In the 4th round, he will likely face #6 Gael Monfils (Rafa leads H2H 12-2). In the QF, he'll likely face his half's remaining toughest seeded opponent, #3 Milos Raonic (Rafa leads H2H 6-2). The SF opponent will be whomever comes out of the mess of the busted Djokovic quarter, and the highest seeds remaining are #8 Thiem (Rafa leads H2H 2-1) and #11 Goffin (H2H 0-0). Cumulative H2H - Rafa 21, opponents 5. The only thing we have to question is Rafa's fitness if someone takes him to 4 or 5 sets, but the further he goes in the tournament, the better he usually looks.
In the top half, #1 seed Murray beat the #31 seed, Querrey, in the 3rd round, and in the 4th round will play unseeded M. Zverev (Murray leads H2H 1-0). A win will see him have to take on either #5 Nishikori (Murray leads H2H 8-2) or #17 Federer (Federer leads H2H 14-11) in the QF. A semifinal is shaping up to be against #4 Stan Wawrinka (Murray leads H2H 10-7). Cumulative H2H - Sir Andy 19-9 if Nishikori beats Federer, or Murray with a slim 22-21 advantage over his opponents if Federer wins, not so easy for the top seed.
#4 seed Wawrinka, beat #29 seed Troicki in the 3rd round, and like Murray, plays an unseeded player in the 4th round, Andreas Seppi (Stan leads H2H 8-3). Then in the QF, Stan has either #12 seed, Tsonga (Stan leads H2H 4-3), or unseeded Dan Evans (Stan leads H2H 1-0). A semifinal shapes up to be #1 Murray (Andy leads H2H 10-7). So Stan has a 19-16 H2H adv. should Tsonga win or 16-13 if Evans takes it. Slim lead and he has a slam winner in his path with a better record.
#17 seed Federer beat #10 seed Berdych in the 3rd round, but in the 4th round faces #5 Nishikori (Federer leads H2H 4-2). Should he get past Nishikori, the QF looks like he will play the now world #1 Andy Murray (Federer leads H2H 14-11). If he somehow managed to win that, then the SF looks like #4 Wawrinka (Federer leads H2H 18-3). It's a challenge for Federer getting to the semifinal, and even with the lopsided H2H, Stan is no gimme now at the Australian Open. Federer has a 18-13 H2H advantage against Nishikori and Murray, but they are both in the top 5 and this is his first tournament in 6 months. Berdych was a good win for Federer, but Nishikori is at least a level or two above Berdych (if healthy), and Murray is of course top level. Federer's advantage with Murray in slams and since 2014 is good for him, but again, is he ready after the time off? It is a big question mark.
I like Murray's chances if Nishikori beats Federer, and Stan's chances if Federer beats Nishikori. It's tough to see Federer beating all 3 top 5 seeds in his first real tournament back.
For the final, Rafa and Stan are both former winners of the AO. Sir Andy remains without a title down under.
If it is Rafa vs. Stan, I would favor Stan slightly. If it is Nadal vs. Murray final, I think it is a toss up, maybe a tiny edge to Nadal. But in either case, I would want to reevaluate once the finalists are known.
Let us see what happens. Maybe some player(s) will break through and crash the "Big 4 or 5" party and my analysis.
Respectfully,
masterclass