I think I’m like most baseball fans in that when I think of a designated hitter, I think of home runs. The DH spot has usually been filled by power hitters since its inception in 1973, and that makes sense. If a player is playing a position with no defensive value, he needs to produce on offense. Home runs are the most valuable offensive event. The most valuable hitters in any given year usually have plenty of home runs and extra base hits. One often hears that a player who doesn’t hit for power doesn’t have the bat to play on the “easy end” of the defensive spectrum, and and even moreso in the case of a player who is primarily a DH. Billy Butler is a current example of a player who mostly fills the DH spot, but since he hasn’t hit for much power (yet), you will sometimes hear people say that he doesn’t fit the profile of a DH. Without focusing specifically on Butler, I’d like to write briefly about what it means to “hit well enough to be DH,” and then to see how often that actually happens with a relatively low amount of power.
Of course, a player doesn’t have to be that great of a hitter to have some value, even as a full-time designated hitter. He just has to be above replacement level. In the model of Wins Above Replacement (WAR) used here at FanGraphs, among position players there is no such thing as a “replacement level hitter” or “replacement level fielder,” just a “replacement level player.” All of the varoius components of a player’s value — hitting, fielding, baserunning, position, etc. — are baselined against the league average. Replacement level for positions players is defined here at Fangraphs as being 20 runs (about two wins) below average, so if all those components add up to greater than minus 20 runs per 600 plate appearances, the player is above replacement level.
What we are interested in here is the positional adjustment for the DH. When a player DHs, by definition he has no defensive value. Without getting into the issue of the “DH penalty” for the difficulty of DHing, the basic conclusion drawn by Tangotiger (he uses 2.25 wins per 700 plate appearances, which is pretty close to 20 runs per 600) is that a league average hitter with no position is a replacement level player. In other words (without concerning ourselves with the difficulty of DHing), to be “good enough” to be a replacement level DH, the player needs to be a league-average hitter. If we (somewhat arbitrarily, given that below-average-but-above-replacement-level players have value) say that a player is “good enough” to start regularly if he is league average, then a player hits well enough to DH if he is 20 runs above average per 600 plate appearances on offense.
Getting back to the original point, when someone says that a player has to hit for power to be valuable to be a DH, assuming they mean at least average by “valuable,” they might be taken to imply that a player can’t (or is not likely to) be 20 runs above average (which we can measure using wRAA and it’s park-adjusted variant “Batting”). How can we check this out? The nice thing about linear weights-based metrics like wOBA is that they get away from confusions about the relative value of batting average, on-base percentage, slugging, power, speed, and so forth, and properly value each event. What this lets us do is to take a pool of hitters and see how often they manage at least 20 Batting (park-adjusted wRAA) runs above average prorated 600 plate appearances without hitting for a ton of power.
Since we’ve already mentioned Billy Butler, let’s take his .151 ISO (he had 15 home runs in 678 plate appearances) as our cut off point. Since the 1973 introduction of the DH, there have been 5,115 player seasons of at least 500 plate appearances. Of those 5,115, 1,541 have been player-seasons where their prorated batting runs per 600 plate appearances have been 20 runs above average or more — good enough to be an average DH (for the sake of simplicity, I’m leaving aside changes in replacement level over time). Of those 1,541, 215 have been seasons with an ISO of .151 or less. Now, 215 is only about 4 percent of 5,115, or about 14% of 1,541, but it clearly does happen.
Among the players who managed multiple seasons of offense worth (well) over +20 runs per 600 plate appearances: Wade Boggs (eight times — he had over a .225 ISO only once in his career, his next highest was .148, and his next highest was .129), Tony Gwynn (six), Rod Carew (six), Rickey Henderson (six), Tim Raines (five), and Paul Molitor (seven). Those are all obvious (at least to me) Hall of Famers. There are some lesser lights as well who make appearances: Julio Franco (three), Willie McGee (twice), and even good John Kruk (once, in 1992, when he hit .323/.324/.458 for a 151 wRC+ with only 10 home runs).
Of course, most of these players had positions, but that isn’t the point. Even if Wade Boggs was a DH-only player, do you really think he would have hurt the Red Sox with his 60 runs above average in 1988, even though he had only 5 home runs in 719 plate appearance? Would Rod Carew’s 42 Batting runs above average in 1974 have not been valuable at DH since he only hit 3 home runs that season? Sure, both those players were more valuable than they would have been as mere DHs, but those seasons obviously would have been valuable even if they hadn’t played the field. A lot of these players (such as Henderson and Raines) had a lot of speed, which, to go back to our earlier example, Billy Butler doesn’t. But: a) stolen bases, even for a great basestealer, only add a few runs a year, and Henderson and Raines probably would still been on the list at least a few times without steals, and b) it obviously isn’t the case for players like Boggs and Kruk. One might be inclined to say that many of those seasons had a more restricted offensive environment, but the truth is that only a few had a league average wOBA lower than 2011′s current .315, and those aren’t by much.
Most full-time DHs are likely to be power hitters because that is the most common source of above-average offense players. But with linear-weights based statistics now commonly available in various forms, it’s time to stop saying that a player has to have power (or some other offensive profile) in order to be a full-time DH. A simple application of linear weights to history shows that to be a false assumption.