MLB second baseman tiers: Shrinking defensive role changes expectations

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Teams have very gradually asked more offensively from second basemen over the decades, a slow-moving trend that dates back to the 1950s. Lately, though, you have to wonder if that's the only thing that's changing at the position.

One undeniable trend is that second basemen hit for more power than they used to. According to positional data from Baseball Prospectus, dating back to 1951, this been an up-and-down proposition over the years, but it has settled in at the upper end of the roller coaster.

In 1951, those who played most of their games at second base accounted for 7.68 percent of all homers hit. That number began to decline immediately from there, dropping all the way to a low of 4.71 percent by 1972. There wasn't a single keystone player to hit even 20 homers in a season from 1968 to 1972. In fact, it happened only twice during both the 1950s and 1960s.

Then things started to change -- slightly -- with the maturation of slugging second basemen like Davey Johnson, Joe Morgan and Bobby Grich in the 1970s. Still, that 1951 homer apex of 7.68 percent wasn't matched again until 2001, when it hit 7.73. There was a one-year dip in 2002, but in each season since then, second basemen have accounted for at least 8 percent of homers.

We reached peak second-base slugging in 2016, at 10.43 percent, more than a twofold spike over the 1972 nadir. A record 13 primary second basemen topped 20 homers in 2016, nearly half the regulars in baseball. That number -- 13 -- matched the total of all keystoners to surpass 20 homers from 1951 to 1984. In 2016, second basemen hit more total homers (585) than catchers, shortstops, center fielders and designated hitters. They also set a new mark for the position by accounting for 12.4 percent of all runs created.

However, the trend has begun to ebb. The homer total for second basemen has fallen from 585 to 558 to 509 over the past couple of years. The share of runs created has fallen to 10.9 percent. Why?

That's hard to say, and it's too early to even call it a true reversal in the trend. The offensive levels for second base remain much higher than they've been for much of baseball history. It's not a matter of moving players around. Twenty-one second basemen had enough plate appearances to qualify for the batting title in 2018, the highest total in 11 years.

You might think that the pendulum is swinging back toward defense at the spot, but that brings us to another, perhaps less detectable, trend: Second basemen are also doing less on defense.

Total chances for every position except catcher are at lower levels than they used to be. Based on data from FanGraphs.com, here is the difference in chances per game for each position, with 1956 compared to last season:

P -0.56
C 3.22
1B -1.05
2B -1.20
SS -1.13
3B -0.60
LF -0.05
CF -0.28
RF -0.20

You probably have already guessed why this is. The relentless climb of strikeout levels has meant less action for every defender on the field, at least those without a face mask and a chest protector. Combine that change with the more recent heightened emphasis on fly ball hitting, and infielders are disproportionately affected -- no position more than second base.

Generally speaking, there have always been around 3.3 infield fielding chances for every outfield chance. That ranged up to 3.7 or so for most of the pitching-heavy 1960s, but has dropped to below 3.2 for most of the past decade. However, last season that ratio dove to a record low of 3.01, down from 3.16 in 2017. With any further decrease, we'll dip under 3 for the first time.

Second basemen handled 15.52 percent of all non-catcher fielding chances during the 2018 season, the lowest figure ever. (Or at least since 1956, the first season for which we have a full data set.) The figures for shortstops are at an all-time low as well, but the drop hasn't been as severe.

What is going on? Could the shift have anything to do with this?

Well, it almost certainly does. While shifts still account for only a portion of total defensive configurations, there simply didn't used to be so many second basemen playing shallow right field. There didn't used to be so many shortstops playing behind the second-base bag, or often to the first-base side of it. Fielders are just not positioned where they used to be positioned.

The bottom line is that second basemen are handling less of a defensive load than ever before, which in turn makes fielding a slightly less crucial aspect of valuing them as a player. We've seen that in play, with teams like the Dodgers and Brewers at times de-emphasizing range at second base, instead looking for offensive production and leaving the run-prevention part of it to the guys who are generating the hitters' spray charts.

It appears that in 2019 baseball, the once-hallowed ability to turn a double play has become marginally less important than the ability to turn around a fastball and drive it into the seats. And the ability to range behind the back of second base as Roberto Alomar once did is now less important than knowing how to read the positioning chart on your wrist as the count changes.

Is this better baseball or worse? Probably it's neither. It's just different. In any event, the qualities that once were trademarks of the best second basemen don't appear to be the quite the same ones teams are using to evaluate the position in today's game.