One bit of conventional wisdom in baseball is that talent tends to be evenly distributed among the different positions. This is more myth than rule because shortstops and first basemen aren't born; the people running baseball teams choose whom to play and where. David Ortiz probably would have been a terrible shortstop, but there was no law of physics preventing the Red Sox from calling Big Papi a shortstop.
Sometimes this talent distribution can change rapidly, reflecting a trend or a truth about what's going on in baseball. For example, when home runs became a powerful point of differentiation among players after the end of the dead ball era, which had been mostly about batting average, the smaller players at second and shortstop didn't add as many homers as the generally larger outfielders did. Same goes for third basemen, the hot corner being considered more of a defensive position than it is today.
Another trend is the decline in difference between players on the hard and easy side of the defensive spectrum. While the importance of talent up the middle to a team was always something you heard in baseball, it has been only since "Moneyball" that the WAR contribution from the middle positions (C, 2B, SS, CF) has finally caught up to the value from the corners. Before 2010, when up-the-middle WAR represented 50.1 percent of the overall WAR (FanGraphs flavor) in the league, the middle positions had passed the 50 percent mark only five times in 109 years, going back to 1901. From 2010 to 2017, it happened in six of the eight years.
You can also see the effect of baseball throwing off the traditional idea that any offensive contribution from a position is just the cherry on top. Teams don't generally throw in the towel on offense from any position these days unless they can help it. It would be much harder today for a player like Johnnie LeMaster, who put up a 66 OPS+ over 3,000 plate appearances from 1978 to 1984, to persuade his team not to research better options.
If you think there's a lot of talent at shortstop now, you're right. Corey Seager, Carlos Correa, Francisco Lindor, Xander Bogaerts, Trea Turner, Addison Russell and so on are a lot of big names. Ten shortstops had three-WAR seasons in 2017, and five shortstops reached the five-WAR mark. From 1976 to 1980, only three shortstops total had a five-WAR season: Robin Yount in 1980, Mark Belanger in 1976 and Roy Smalley in 1978.
And it likely won't stop any time soon. Projecting out five years for current position players in professional baseball, the shortstop talent level looks to continue to increase relative to other positions. It's not surprising; the star shortstops today aren't just good; they're also very young.
Now, you would expect shortstops on average to be young (players move to easier positions as they age), but from the 2018 ZiPS projections, the top 15 shortstops are more than two years younger than the top 15 at any other position.
ZiPS projects only a single shortstop in the top 15 in 2018 as a member of the over-30 set, Brandon Crawford. The second-oldest shortstop in that group is Andrelton Simmons, who turns 29 in September. To find other over-30 shortstops, you have to get to Troy Tulowitzki (21st) and Jordy Mercer (23rd). And more are on the way: Of Keith Law's top 100 prospects for 2018, 10 are shortstops.
On the flip side, the left-field talent pool is as thin as it ever was. ZiPS projects only 10.3 percent of WAR this season to come from left fielders, the second-lowest number since 1901, just barely beating out the 10.1 percent from 2016. In 1930, starting in left you had Al Simmons, Heinie Manush, Goose Goslin, Chick Hafey, Babe Ruth/Earle Combs -- all Hall of Famers -- and Lefty O'Doul and Wally Berger, who aren't really that far off. In 2018, ZiPS doesn't project a single left fielder for a four-WAR season (tops is Marcell Ozuna at 3.7 WAR).
If you're a fan of today's crop of young shortstops, Cooperstown looks like it will be a fun place to visit somewhere around 2035 to 2040. The current shortstops look to heavily invade the all-time shortstop rankings, according to WAR. Let's finish up with what that ranking is projected to look like 20 years from now (obviously missing anybody not currently in professional baseball). Honus Wagner is untouchable as the all-time leader at 130.9 WAR, and Cal Ripken (95.9) and dead-ball-era star George Davis (84.9) might seem out of reach. But Correa already projects fourth all-time at 77.6 total WAR, nosing out Robin Yount (77.3) and Ozzie Smith (76.9), and then Lindor is projected to finish seventh with 76.6. Seager projects to 70.5, outside the top 10 but bracketed by Hall of Famers Alan Trammell and Barry Larkin. And ZiPS projects Simmons to finish among the top 20 with 62.5 WAR.
So the present at shortstop is already very good, but the future? It should be glorious. Buckle up and enjoy the ride.