*Note: I spent a while writing this and then my tab reloaded and lost the whole thing, so what follows is a reheated version:
Neither Stefanos Tsitsipas nor Karen Khachanov finish in the Top 10
Both young guys are among the 5 most hyped ATP prospects, and both made big charges last year (Tsitsipas in the middle of the season, Khachanov in the post-Wimbledon hardcourt seasons), but development isn't linear and each still have significant concerns.
Saying Khachanov struggles on the fast courts feels a bit unfair since his loss to Juan Martin del Potro in Australia last year might have been the match of the men's tournament (and contributed to Delpo's surprise beatdown at the hands of Tomas Berdych afterwards), but it is still true.
If he is to make the top 10 in 2019, the spring will be critical for him, since Indian Wells should work for his game, he has the physicality to succeed in Miami, and he's shown flashes on clay.
Tsitsipas is a tough omission because he has the whole toolkit, save for a strong return game. The problem is that returning is a critical skill. In 2018, Tsitsipas played 49 tiebreaks in 84 matches. For comparison, Sascha Zverev played just 23 in 77 matches.
The good news for the future champion is that he should fare better that 23-26 in breakers this year. However, his Rogers Cup breakout was driven by winning a lot of razor-thin margins in succession, so while he should see positive regression with luck overall, a lot of it concentrated in 2018 to deliver a 600 point result that may not be there in the immediate future.
Nikoloz Basilashvili does finish in the Top 10
Basilashvili is the ATP equivalent of comparing a low-level draft pick in basketball or football to a highly touted prospect and wondering when the body of work should outweigh the pedigree.
The late bloomer might be turning 27 next month, but his game seems absolutely miserable to play against with some of the heaviest shots on tour off both wings, and he has fewer holes in his game than some of the players ranked ahead of him.
The Hamburg and Beijing champion has shot up the rankings and might be even higher if he didn't run into Nadal, Djokovic, Anderson, Nishikori and Coric when he did in tournaments.
Rafael Nadal wins a non-clay major/Djokovic and Nadal share all 4 Slams
While many think of Nadal's 2017 US Open title as a cheap one, he's been pretty unlucky to only snag one major off the dirt these last couple years, especially at the Australian Open.
Even with Djokovic back, it seems inevitable that if Rafa keeps putting himself in winning positions, the narrow margins will shift back his way again.
I officially picked Nadal to win AO and RG, Djokovic to repeat at Wimbledon and the US Open, but I think Rafa has a similar chance to win each of the non-RG Slams and don't feel strongly about which one (or ones) he ultimately wins.
Barring injury, those two are far superior to the field.
Novak Djokovic's serve numbers decline
From Queen's through the ATP Finals, Djokovic held at an astounding 91% clip (and still 90.3% excluding grass and starting at the Rogers Cup).
For perspective, he held serve 88.2% of the time on hardcourts in 2015, and 88.8% from Doha through Miami in 2016, a stretch in which he went 28-1, his only loss coming via retirement to Feli Lopez in Dubai.
Much like I predicted for Nadal at this time a year ago, I just don't see Djokovic keeping that high of a rate, and that has nothing to do with predicting his decline as a player.
The early returns back this up, with Djokovic holding at 86.8% in Doha.
Simona Halep does not finish #1
The narrative: the Darren Cahill split (even if temporary), her quotes about her priorities and mindset now that she's won a major (which could also be argued as a good thing, to be clear).
The history: the only women to threepeat as #1 are the WTA Mount Rushmore - Evert, Navratilova, Graf, Williams - and for as good as Halep is, she's not them.
Angie Kerber does
When picking an alternative to Halep, I found it best to do process of elimination.
Durability: Wozniacki, Osaka
Consistency: Stephens, Osaka again, Muguruza
Light schedule: Williams
Lack of Slam points: Kvitova, Svitolina, possibly Wozniacki
Not all of those labels will pan out, but the point is that I felt it was pretty hard to find contenders for the top spot besides Kerber and Aryna Sabalenka.
The youngster is a beast on hardcourt and projects to mow through her fair share of tournaments, I just gave the edge to Kerber figuring she'll stack enough volume with her heavy schedule to offset Sabalenka's, and she has the proven ability to peak for and go deep in all the Slams.
Stan Wawrinka finishes Top 15 but not Top 10
Two reasons:
1. The back half of the ATP top 10 projects to be deeper than the last couple years.
2. Stan the Man's low ranking could mean that even if he plays at a top-10 level, rough draws might artificially deflate his true ranking.
Two Grand Slam champions retire after 2019
Aga Radwanska was the surprise retirement of 2018, and while Jon Wertheim makes a good point about the marketing allure of the Tokyo Olympics, the current situations of Andy Murray, Venus Williams, Maria Sharapova, Caroline Wozniacki, and Svetlana Kuznetsova mean there's a good chance that a couple Hall of Famers walk away before the end of the decade (with fringy HOFer Sam Stosur also in that group).
Sascha Zverev does not reach his first Grand Slam final
Zverev's best surface is clay (while his level on hard makes it debatable, it's still clay compared to the level of the overall tour), yet his game doesn't cater to Roland Garros.
I would argue Zverev is clearly a superior player on clay compared to his buddy Dominic Thiem, yet it doesn't really matter when Thiem's weapons can mow through the first week and Ivan Lendl's pupil has to grind out lesser players, leading to Domi having much more energy to finish the tournament.
It's sensible to think Zverev's first Slam final is around the corner, but without a clear path at the French Open, it's significantly harder to actually pinpoint where it happens.
Alex de Minaur finishes Top 15
Though The Demon's game has some long-term concerns as to whether his size can win majors, de Minaur is ahead of the curve that peers like Khachanov and Daniil Medvedev are on, and I'll predict him roughly matching them in rank straight up.
The same could be said of Denis Shapovalov, who isn't 20 until April, but being the best young returner in years gives the Aussie a bankable edge over Shapo for the immediate future.