Patrick Mahomes, during his storybook 2018, set a record for fantasy points by a quarterback in a single season, putting up 417.1.

Mahomes' 50 passing touchdowns tied for the second-most by any player in NFL history, and his 5,097 passing yards was eighth-best. The Kansas City Chiefs star was only the second player in history to manage at least 4,500 yards and 45 touchdowns passing at the age of 23 or younger, joining Dan Marino (1984).

By all accounts, Mahomes' breakthrough 2018 set him up for one of the most promising careers in the game's long history, and there's absolutely no disputing his standing as fantasy's top selection at his position.

Except that I dispute it.

Deshaun Watson is the quarterback I'd pick to lead the position in fantasy in 2019.

A lot of it has to do with the effects of statistical regression on Mahomes' numbers, which we'll get to in a bit. But this is as much about Watson's skills improvements during his own two NFL seasons to date, as well as the Houston Texans signal-caller's own expectations.

What the numbers say

Watson's 331.7 fantasy points last season ranked fourth at the position, 85.4 behind Mahomes and also behind Matt Ryan's 355.0 and Ben Roethlisberger's 341.9. That was the 34th-best single-season total by any quarterback in NFL history, but it was lost in the shadows of Mahomes' banner year.

In the process, Watson's performance actually regressed on a per-game basis compared to that of his rookie 2017, but progressed in terms of the cumulative total and also the improvements he made to his game. His 2017 featured 24.1 fantasy points per game, 10th-best by any quarterback in NFL history, and a total of 163.2 points in his six starts -- the first six of his NFL career -- which was 20.6 more than any other quarterback has had through his first six starts (Cam Newton owns that second-best total).

Watson's per-game average dipped by nearly 3½ points to 20.7 as a sophomore, his first full season as an NFL starter. And in the process, his game-changing fantasy performance was seemingly forgotten, replaced by the new "hot hand" at the position. Nevertheless, his output was historically relevant: His 103.1 passer rating was eighth-best and 68.3% completion rate second-best in NFL history among second-year quarterbacks. Those numbers rank fourth and first, respectively, in those same categories among quarterbacks age 23 or younger in a season.

That completion rate represented a key improvement for Watson: More of a "chucker" as a rookie -- a quarterback with no fear of tossing the ball deep despite the risk of turnovers -- he became considerably more disciplined and, with the change, accurate as a sophomore. Here's a breakdown of his passing exploits so far in his career, divided into three parts:

With "air yards" representing the distance his throws traveled through the air beyond the line of scrimmage, Watson's steady decline in the category suggests he has become more selective with his throws. And the decline in touchdown rate has not been the problem you might think, either. It's his substantial drop in interception rate that has made the biggest difference. To that point, 173.7 of Watson's 331.7 points came in the second half of last season.

Yes, you read that right: Watson averaged more fantasy points per game during the second half of 2018 than the first, despite taking fewer deep shots.

Now consider that Watson still has his No. 1 wide receiver in DeAndre Hopkins, one of the very best at his craft in the NFL. And he stands good odds of getting more than the seven and six games played, respectively, by up-and-coming receivers Will Fuller, one of the best big-play wideouts in the game, and Keke Coutee. Little has changed with the Texans' passing attack entering 2019, so there's reason to believe Watson should continue to mature as a passer.

What's more, as he has become a smarter passer, Watson hasn't lost anything from his running game. He was as apt to take off in Week 17 of 2018 as he was in his first NFL start. In fact, his 46 rushing attempts, 276 rushing yards and four rushing scores in his final six games of 2018 (Weeks 12-17) represented his largest totals in any of those three categories during any six-game stretch so far in his career. Watson's 56.1 fantasy point total on rushes alone in 2018 was third-best among quarterbacks, trailing only the 77.6 by Josh Allen, whose per-rush numbers were unsustainable, and 76.6 by Lamar Jackson, who ran more often than any quarterback in NFL history.

2019 outlook

Put it together and it's reasonable to think that Watson could be a 350-point performer in 2019, or perform even better in the best-case scenario. That he's also one of the game's most mobile quarterbacks also elevates his statistical floor/worst-case scenario in a way that few ranked in his tier experience. When it comes to the No. 1 pick at a position, I think return on investment is more important than upside.

Mahomes, meanwhile, will inevitably regress statistically, if only due to the inability by athletes to replicate historically productive seasons. He's the 10th quarterback in the game's history to have scored at least 350 total points and 23 points per game. The previous nine to do it saw their fantasy point totals regress by an average of 23.2%, a rate that would result in a total of 320.3 points for Mahomes in 2019.

Opposing defenses should also be more prepared to devise a game plan for Mahomes in his second full season as an NFL starter. Though his season might have been unlike any other, the history of "breakthrough" quarterbacks illustrates this: Selecting 10 who enjoyed significant breakthroughs in terms of fantasy points (comparing the output to previous career bests) before the age of 30, that group's regression rate was 15.2%, which would amount to a 353.6-point Mahomes campaign.

Mahomes' supporting cast took more hits than Watson's as well, as top wide receiver Tyreek Hill faces a potentially lengthy suspension, and the team's running back picture isn't as clear as it was at the onset of 2018. Mahomes might become easier to plan against with Sammy Watkins as his top wide receiver.

This isn't to say that Mahomes can't come close to his 2018 output, or finish atop his position again in fantasy points. Perhaps he's still the wisest selection at the position, with part of my "draft Watson" angle hinging more on my level of patience selecting quarterbacks: If Mahomes goes 20th to 25th overall in your draft and Watson 45th, I'm taking Watson every time if choosing between them. Frankly, I think both are comparable bets to lead the position in scoring, but with the multitude of productive quarterbacks these days, I don't think either one warrants selection before roughly that 45th overall pick. Watson is much more likely to be a value at his selected spot.

But color me unsurprised if, come season's end, Watson has 30 passing and eight rushing scores and Mahomes 38 and two. And if that's the case, Watson is going to be the one you'd rather have on your team.