Where to start on this fanpost prompt? Let's go back a bit and approach it from before the season began.

Pre-Season Expectations

Before this season began, here's what I thought I'd be watching in 2017:

• Gardner, Ellsbury, Castro, Didi performing close to their career norms (even if they replicated or marginally improved upon 2016)
• Tanaka to carry the rotation, with Pineda and Sabathia providing consistently inconsistent starts and Severino and TBD to follow up the rear with understandably mediocre "learning" seasons as the #4 and #5 in the rotation.
• Matt Holliday to possibly hit close to his career norms (better than 2015 but not as great as his prior years in St. Louis).
• Aaron Hicks to continue his slide into obscurity as he tumbled down the rabbit hole of horrible batting.
• Gary Sanchez to be Gary Sanchez, but not quite as good as 2016.
• Judge to continue adjusting to the league (maybe settling in as league average or possibly much better, since that's what he did at every level of the minors: struggle in his first season after being promoted, then rake in the next season.
• Greg Bird to be the mainstay at 1B and continue his hot hitting from Spring Training (probably the ceiling being an above average bat at 1B while he continues to acclimate himself to major league pitching after a season away from the game).
• Headley being Headley

Current Assessment: Holy Cow! Surprises Abound!

So, all those things I listed above, the only two that met expectations to one degree or another were Sanchez and Judge. But even then, I honestly did not expect Judge to be the major league home run leader, and bWAR leader; and to not only be in the discussion for Rookie of the Year but also now possibly the MVP (and probably going to the All Star Game in his first full season, along with Gary Sanchez). Sanchez, also, on the season, has been pretty much as expected (not the 171 wRC+ monster he was in 53 games in 2016 but a much more realistic 138 wRC+ Kraken that might still be unleashed even further as the season goes on). The 138 wRC+ is much more inline with his minor league career than the 171 was, so that might be his happy medium (and now he doesn't have to try too hard with everyone on the offense clicking so well).

Also, Headley has been pretty much what I expected (nothing great nothing horrible, or not too horrible) and his numbers will normalize to somewhere around league average by the end of the season.

Everything else has been the exact opposite of what I expected:

• The veterans from last year (Gardner, Ellsbury, Castro, Gregorius) are either having or practically having career years at the plate.
• Holliday is hitting much better than even he had in his last few seasons in St. Louis
• Tanaka is the worst pitcher in the rotation; Sabathia has been fairly consistently good but as the #4 performing starter; Luis Severino is LEADING THE TEAM IN ERA and FIP (among starters with more than 1 game started); Michael Pineda is the #2; Jordan Montgomery is the #3 with a very, very nice start to his career (a consistent 3.55 ERA / 3.54 FIP); and did I mention that Tanaka is the team's worst starter (to the tune of a 6.55 ERA / 5.64 FIP)?!
• Aaron Hicks is channelling Aaron Judge and hitting the ball all over the place, defying reason and logic at his performances in the last four years.
• Greg Bird is injured (and before he went on the DL, he was hitting very poorly). Hopefully his Spring Training ankle injury was the source of his poor production.

Plus, the Yankees are in first place by 4 games (at the time of this writing), riding a major league leading run differential of +115 and they've allowed the fewest runs in the AL (and are second only to the LA Dodgers when compared to the whole of MLB).

No matter what happens from here, this season has been the most fun I've had as a Yankee fan since 2009, and the future looks bright (even if some of these guys come back down to Earth).

This whole season has been a surprise, top to bottom.

Go Yankees, Go! You are literally #1!