Andy Reid knew what he was doing.

That was the first thing that popped into my mind when I tried to look back on what I learned about the 2018 NFL season. Not that I ever necessarily thought Reid didn't know what he was doing, but when I think back to last summer, I recall being at least a little bit skeptical about the decision to trade Alex Smith and turn a successful Kansas City Chiefs offense over to an untested Patrick Mahomes. I'm big on having to see it before I believe it, and I just figured Mahomes, like most young quarterbacks, would be prone to some growing pains, and it could set the Chiefs back in the short term. If this were an episode of "Arrested Development," this is the part where Ron Howard would say, "It did not."

2018 NFL Playoffs Coverage From the wild-card round through Super Bowl LIII, ESPN.com has you covered.

• Full schedule, news, notes »

More NFL coverage »

Mahomes just threw 50 touchdown passes for a Chiefs team that went 12-4 and secured the top seed in the AFC playoffs. He's almost certain to win the league's MVP award. He endured no discernible growing pains. Rather, he dominated the league from September through December, and he may well be positioned to deliver Reid his elusive first Super Bowl title.

I've been wondering lately whether Reid needs to win a Super Bowl in order to make the Pro Football Hall of Fame. My guess is he probably does, even if his non-January record of accomplishment is probably the second-most-impressive of his time, after that of the guy in New England. But whether he ever gets that Super Bowl title or not, this is the kind of thing that will come up in Reid's favor when they talk about whether he belongs in Canton.

Andy Reid's decision to hand his offense's reins to Patrick Mahomes wasn't without substantial risk. AP Photo/Ed Zurga

It's easy to love the move now, after seeing how it worked out, but think back. Smith had an MVP-caliber campaign in 2017 for a Chiefs team that went 10-6 and won its division. The logic behind dumping him and switching to Mahomes was that Mahomes would elevate the ceiling at the most important position and that his raw talent offered Reid's offense a chance to function at previously impossible levels -- eventually.

The fact that this happened in 2018 is a testament to Reid's ability to make and execute a plan, to develop a young quarterback and give him the tools he needs to succeed, and to get a group of NFL players to believe in his vision. That's what coaching is all about, and as we swim through this year's head-coaching carousel, it's important to look at the people who are doing it at the highest level and have been for a while. Reid's going to have a lot of marks in his favor when that Hall of Fame conversation happens someday, but Mahomes' 2018 season -- no matter how it ends -- may be his crowning achievement so far.

As for other things we learned in 2018 in the NFL, let's do one per division, so people don't feel left out. The AFC West is already covered.

The Dolphins finished second but are the furthest AFC East team from catching the Patriots

This isn't just because Miami fired coach Adam Gase on Monday. It's a big-picture assessment involving quarterbacks. Ryan Tannehill had every opportunity this year to prove he could be the guy the Dolphins thought they drafted, and he didn't. Miami is set back at least a year at the most important position, while the Jets and Bills exit 2018 feeling very good about the young quarterbacks they drafted. They have more to do to build around Sam Darnold and Josh Allen, but when you believe you have your quarterback, other decisions are much easier. Miami has to find a coach and a quarterback, while the Jets just need a coach and the Bills believe they have both. That puts the Dolphins behind the pack when we're imagining who could take over this division once Bill Belichick and Tom Brady are done with it.

Repeating is hard, no matter how good you look

On this one, I was actually right. There was no reason to think the Eagles wouldn't repeat as NFC East champions except that no one has done it since 2003-04. This is not a coincidence. The division is packed with bitter rivals who never seem to be in rebuilding mode and is perpetually quite competitive. The Eagles had a Super Bowl hangover most of the season and showed a champion's mettle in recovering to make the playoffs as a wild card, but they still finished second to Dallas, meaning that streak lives another year. It would be at least a mild surprise to see the Eagles make a Super Bowl run from the No. 6 seed with Nick Foles, but no one's here to say they can't. Regardless, the position in which they enter this year's postseason reflects how difficult it is to do what they did last year twice in a row. A lesson worth remembering this summer when we're extolling the dynasty prospects of whoever wins Super Bowl LIII a few weeks from now.

The Bears' acquisition of Khalil Mack could be the NFL's most impactful trade of the year. Jonathan Daniel/Getty Images

Some defensive players ARE worth quarterback money

There were two NFC North teams that were supposed to be "one player away" from Super Bowl contention. The addition of Kirk Cousins and the return of Aaron Rodgers were supposed to lead to a killer two-team race between the Vikings and Packers. Instead, the Bears, who'd been quietly building a fearsome defense for a couple of years now, added Khalil Mack right before the season and muscled their way to a division title. Turns out it was Chicago that was "one player away," and that player wasn't a quarterback. The deals that Mack and Rams defensive tackle Aaron Donald signed right before the season were historic, and there are plenty of teams out there (cough ... Raiders) who'd never even think about going north of $20 million a year for a defensive lineman. But there are cases where it makes sense. There were other factors in the Bears' resurgence, including the program that Coach of the Year front-runner Matt Nagy put in place for young QB Mitchell Trubisky. But the addition of Mack at the most hopeful time of the year changed everything in Chicago.

DO NOT judge these head-coaching hires this month

Nagy's toughest competition for Coach of the Year may be in Indianapolis, where the Colts are being coached by a guy who wasn't even on their interview request list this time last year. You surely remember the Colts agreeing to a deal with Josh McDaniels only to have McDaniels back out after the Super Bowl. The Colts turned to Frank Reich, who turns out to have been the absolutely perfect guy to manage Andrew Luck's shoulder recovery and keep a young team on track after a 1-5 start. (The Colts had just an 8.5 percent chance of making the playoffs after Week 6, according to ESPN's Football Power Index.) That the Colts are in the playoffs is a stone miracle, given their personnel, and it's the achievement of a coach they had absolutely no intention of hiring when the hiring season started last January. It's a little bit like the Eagles hiring Doug Pederson after Ben McAdoo turned them down. We'll rank the head-coaching hires when they're all done, but we'll be guessing.

Baker Mayfield and Lamar Jackson could be battling for AFC North supremacy for the next decade. Patrick Smith/Getty Images

The 2018 QB draft class may just have been special after all

Did anyone else get a huge kick out of watching the Baker Mayfield Browns and the Lamar Jackson Ravens play each other Sunday? Think about those two going against each other for the next decade or so in the AFC North. Jackson needs to refine himself as a thrower, but he clearly has ability in that area, and his running makes him a breathtaking player to watch. Mayfield's toughness and accuracy are great attributes, but more than that, he seems to be the perfect fit for his town. No one's thought much of Cleveland for a while in NFL circles, but Mayfield, quite aggressively, does not care what anyone thinks. We wait to see who'll be coaching him, but he looks like the real deal so far. Outside this division, Sam Darnold and Josh Allen finished the season in extremely promising fashion, and Josh Rosen had his moments in a terrible situation in Arizona. All five teams are fired up about the guys they picked.

A winning coach/quarterback combo can last a long time

The Seahawks were supposed to be done, remember? Legion of Boom all gone, offense stuck in the mud, Pete Carroll changing coordinators all over the place ... this was supposed to be the year Seattle started its rebuild. The Seahawks instead went 10-6 and made the playoffs. They finally put together a real run game. The young guys they developed on defense to take the place of those departed championship stars blossomed in key places. The veterans who remained played hurt, played their tails off and led by example. But the foundation here is a quarterback in Russell Wilson who never lets his team believe it's out of a game and a coach in Carroll who trusts in the solidity of the program he has built even as the names on the backs of the jerseys change. The Seahawks went into this season expecting to win, and they did.

Heartbreak can be a building block

The 2017 Saints were good. Maybe even good enough to win a Super Bowl. We'll never know, because the Vikings snatched that chance away from them with a miracle touchdown in the playoffs. But sometimes that kind of thing can galvanize a team, and for whatever reason, the 2018 Saints appear to be even better. With a varied and dangerous offense to go with a burgeoning defense, New Orleans enters the playoffs as the favorite to win it all. We could have done that last coach/QB item about Sean Payton and Drew Brees just as easily. And when we're talking coaching candidates, it's fair to expect teams to be interested in Saints assistants like Dan Campbell and Dennis Allen this hiring cycle. There's a whole bunch of good stuff happening in New Orleans, and the Saints are three wins away from overcoming the memory of the way last season ended for them.