Last season, second basemen produced their best collective season ever in major-league history. There are a few different theories about what might have happened. With the increased use of the shift, it’s possible that teams were willing to deploy worse defenders at second in exchange for more offensive production. It’s also possible it was just a random blip of very good seasons by quite a few second basemen. Those are the most likely explanations, at least.

We’re now roughly halfway through the 2017 campaign, and the production from second basemen so far has been good — one of the better seasons of all time, if things hold up — but it also represents a big step back from what we saw last year.

How big a step back? Well, consider: last year, 11 second basemen recorded four-win seasons.

In contrast, here’s the list of players who are projected to hit 4.0 WAR by the end of the current season.

Second Basemen in 2017 Name AVG OBP SLG wRC+ WAR ROS Projection EOS Projection Jose Altuve .328 .402 .527 150 3.5 2.3 5.8 Daniel Murphy .339 .391 .578 146 2.4 1.6 4.0

Even if you include the players who are “on pace” to hit four wins — if not forecast by the projections to do so — then the only additions are Josh Harrison (2.3 WAR as of Sunday) and Jed Lowrie (2.1 WAR).

It’s not just overall value that’s taken a step back, either. If you look at the first table from this post, you’ll see that nine second baseman recorded at least a 120 wRC+ last season. Matt Carpenter — who split time evenly between second, third, and first — would make a 10th. Nor does that include the 122 wRC+ or 3.7 WAR produced by Neil Walker, as he fell roughly 50 plate appearances short of qualifying for the batting title.

So far this season, only six second basemen have produced a batting line above 120 wRC+. Only two other players are close. So what happened? Jose Altuve is still doing what he does, as is Daniel Murphy. As for the rest:

Robinson Cano is now 34 years old, so expecting him to remain elite is a bit too optimistic.

Brian Dozier has had some injury struggles and is just an average hitter this season.

Ian Kinsler is 35 years old and has returned to the levels he’d established before 2016.

The 33-year-old Dustin Pedroia has seen his power and BABIP erode, rendering him just an average hitter.

Jean Segura doesn’t play second anymore.

Jason Kipnis started the season on the disabled list with a shoulder injury and hasn’t really recovered.

Cesar Hernandez’ .363 BABIP from last year has predictably regressed, and the Phillies’ second baseman is now out a month or more with a strained oblique.

The 36-year-old Ben Zobrist has dealt with injuries, as well, and hasn’t hit this season.

DJ LeMahieu’s near-.400 BABIP hasn’t held up this season.

It’s not too hard to find a pattern here. Age and injuries have dealt the position a blow this season, and no players have emerged where those players have fallen. Starlin Castro is having a solid year and Harrison and Lowrie were mentioned above. After that, though, you have Brandon Drury, Dee Gordon, Whit Merrifield, Joe Panik, Brandon Phillips, and Yangervis Solarte all hovering around average.

This isn’t to say, of course, that second basemen have played poorly this year. It’s been quite the opposite actually. If you want to look historically at how second basemen have hit over the last 40 years, the numbers still look decent.

The 93 wRC+ produced by second basemen this year represents a big drop from last season’s 101, but it’s better than the 50-year average mark of 88 wRC+ and still above the average of 92 over the last 20 seasons.

I will note one thing — namely, that those historical figures account only for players who are classified as second basemen in our database. In other words, not every player included in the sample was necessarily a regular second baseman.

Starting with data from 2002, we can be a little more precise and look only at the numbers a player recorded while actually playing second base. In that respect, the position’s numbers are even better.

Second baseman are still hitting a lot better compared to the rest of the league than they have in the recent past. Here’s how second baseman have hit relative to the rest of the positions in baseball.

There’s the second basemen right in the middle of center fielders and third basemen. All three happen to have the same positional adjustment at +2.5 runs per season, although we’ve generally come to expect far less production from second base. We think of third basemen as sluggers and see some of the best stars in the game at third — Nolan Arenado, Kris Bryant, Manny Machado — but third baseman have historically put up average offensive numbers and that hasn’t changed this season.

First baseman have been the biggest beneficiaries of the increase in scoring and home runs; they’re putting up better numbers than we’ve seen from them in more than a decade. Shortstops and catchers are down at the lower end just like they always are, although shortstop experienced a great year in 2016 that has also declined a bit this year. Designated hitters are suffering after losing David Ortiz, though he only accounts for about three points of the 11-point drop in wRC+ this season. Perhaps the most surprising development revealed by the graph above is the lowly production recorded by left fielders. That said, this isn’t really new, either. A decade ago, left fielders were 5% to 10% better than the rest of the league and were still above average earlier this decade. The last few years, however, they’ve barely been average at all.

Second baseman aren’t repeating the great season they had last year, but it was unfair to expect them to. In 2016, they were historically great as a position and multiple players in the midst of their decline phases had very good seasons. That was bound not to be sustained. Despite dropping a decent amount from last season, the position is still hitting quite well compared to historical standards for second basemen, as well as the rest of the positions in baseball. We will need to monitor the position for the next few seasons, but it’s certainly possible second base will be a more offensive-minded position in the future, even if the group never reaches its 2016 levels again.