Dan Johnson's hit fairly well so far this year. He's put up a wOBA of .339 and wRC+ of 115 in 140 PA, good for 2.4 wRAA. This doesn't seem that abnormal, until you notice that his batting average is a tick below .200 (.198) thanks to an even lower BABIP of .188. A BABIP of .188 is obviously unsustainably low. In fact, Johnson's BABIP of .188 is the lowest amongst hitters with more than 100 PA. It's very very difficult to be a productive hitter with a BABIP below .200. In fact, Johnson is the only hitter that's been above average with a BABIP below .200. When we raise our BABIbar™ to .250, the list of productive increases. Barely.
There are only 6 hitters (min 100 PA) who have succeeded at all while having such an extraordinarily low BABIP (including our very own Carlos Pena), and none of them are anywhere near Dan Johnson levels. While the majority of these hitters walk at above rates, two of them (Encarnacion and Sweeney) don't. The distribution of strikeout rates amongst them is almost entirely random as well. The one category in which they all succeed (and indeed for which many of them are known) is power. They all have above-average slugging %s despite largely unlucky batting averages, and they all are well above-average in terms of ISO (isolated power). Indeed, Dan Johnson's .216 ISO is about 1.5 times league average, and powered by a Mark Teixeira-esque HR/FB of 17%.
Even among these hitters, Dan Johnson's BB% of 17.9 makes him an outlier. Johnson is 4th in BB% among hitters with 100 PA. He walks more than one in every 6 plate appearances. If This is obviously an unsustainable level (the league leader over the last 3 years is Chipper Jones, who has a 16.7 BB%) but what can expect going forward?
Since plate discipline statistics stabilize much more quickly, it makes sense to try to project Dan Johnson based off of those. Using the methodology we see in the last link, we see that Johnson's walk rate is still an earth-shattering 15.1%. This isn't surprising, given that Johnson has the 8th lowest O-Swing% in the AL and the 16th lowest Zone%. That being said, his incredibly low Zone% of 42.1 is probably not a sustainable. Only Vlad Guerrero has one lower than 43% over the last three years. Pitchers will probably begin to attack Dan Johnson when they realize he isn't chasing. If we regress his zone% halfway to league average (power hitters have below average zone%s although the amount of regression is arbitrary), then he'd still have a BB% of roughly 14.5%. Dan Johnson's plate discipline is very real.
Using Jack Moore's ffwOBA, we regress his BABIP to his career mark of .250 and his BB% to the 15% mark that's projected (CHONE says that his ISO thus far has been roughly what we can expect going forward), and arrive at a wOBA of roughly .365. From the DH hole, this would mean a ~2.2 WAR player. Dan Johnson might not be the next Albert Pujols, but going forward, he looks to be a productive contributor to the Rays.