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You don’t need me to tell you that the rate at which a hitter makes contact with the baseball is integral to his value but hopefully you do need me to tell you who is getting better and worse at it, because that’s what I’m about to do.

Examining changes in contact rate can help explain the 2014 struggles of JJ Hardy and Brandon Belt, or the 2014 improvements of Christian Yelich and Ike Davis, for example. The analysis isn’t reserved for players close to the margins of standard fantasy league relevance. A decrease in contact rate partially explains Bryce Harper’s good-not-great 2014 while a marked increase helped propel Yasiel Puig into fantasy stud territory.

Given that contact rate stabilizes relatively quickly, it’s something that warrants in-season monitoring. It’s worth remembering an important caveat about what the stabilization thresholds actually tell us so we can avoid the common trap of using them incorrectly. To quote Russell Carleton, who wrote the seminal piece of research on this topic:

“Here's how to understand those stabilization points. Suppose I was doing research on Smith and other MLB players and I needed some estimate of what his true talent on K rate was during the last month. I certainly can't take a one-game sample. I need something a little bigger, but how much bigger? Well, the answer to that is it takes about 60 PA until the sample is ‘good enough’ for the purposes of research. So, if I wanted to tell you what I thought Smith's abilities were back in April when he amassed those 60 PA, I'd say that I have a reliable enough sample to say something meaningful about what he was back then. This is not the same thing as saying that I expect him to maintain that same true talent level in May, plus or minus some noise. It's not a silly assumption to think that he will do the same in May, but it is an assumption. It's not even the same thing as saying ‘I now know what Smith's true talent level was in April.’ Even then, I'm only giving an estimate that meets certain statistical standards for ‘probably pretty close.’"

So, I can’t tell you with any authority that these contact rate changes represent a permanent shift in true talent level. What I can do is try to help understand the underlying context and offer my opinion on whether the change might have some staying power. Here are my thoughts on five of 2015’s biggest movers:

Danny Espinosa, 2B, Washington Nationals: 12.16% change

The impermanence of Espinosa’s preseason mustache all but shattered my belief in a Divine Being. I believe in second chances, so I'll settle for inability to change his current profile picture, which features a knowing smirk behind a squirrel’s tail on a man’s face. Your move, Ma’am. The Nationals must also believe in second (third?) chances. Good thing for Espinosa, considering he followed up a 2013 spent floundering in Triple-A with a .634 OPS as a part-timer in 2014. Espinosa sunk so low that the Nationals, a World Series favorite, opened the year with Dan Uggla as their starting second baseman and Espinosa as his short-side platoon partner. With Anthony Rendon disabled, Espinosa parlayed a hot start into regular at-bats between the keystone and the hot corner and he's kept on hitting. His 78.29 percent contact rate is an easy career high and an extreme improvement over last year’s career low. Espinosa still comes to the dish swinging before Ronnie Van Zandt even finishes singing that Busch commerical and while his career best contact rate on pitches in the zone is noteworthy, the 18 percent year-over-year improvement on pitches off the plate is most eye opening. Espinosa has whiffed less against all pitch types but his rediscovery of a league-average ability to hit fastballs is driving much of this change. It's wise to expect some modest regression in all three components of his .252/.354/.450 triple-slash and his K:BB will widen but that won't sap all of his fantasy value if he can hold some of the contact gains and remember how to steal a base. Playing time is a question but Espinosa has started four of the six games since Rendon's return and there are reports that he could see time in left field with Jayson Werth on the shelf until August.

Rajai Davis, OF, Detroit Tigers: 8.90% change

It isn't too often that a 34-year-old improves a core skill four years running, but that's exactly what Davis has done. Beginning with his career low 76.92 percent rate in 2011, Davis inched up in 2012, 2013, and 2014 and has taken a massive leap forward this year. His current 92.31 percent rate is fourth best in baseball among players with as many plate appearances. Davis' gains are largely the result of chasing fewer pitches outside the zone. When he does swing, his contact rate is dramatically better than it ever has been and on par with some of the best contact hitters in the game. Davis has exhibited a pattern and I'm comfortable acknowledging that some of this is a result of an evolving approach. Even if he gives some of it back, his speed, a little more luck on balls in play, and frequent position atop Detroit's batting order will keep his value steady. There's risk of losing at-bats to Anthony Gose as the year wears on but with Victor Martinez banged up, Detroit has found a way to keep Davis in the lineup more often than not.

Yasmani Grandal, C, Los Angeles Dodgers: 7.38% change

Unlike the two players above, this one may just be a case of a talented young player blossoming in to the player many thought he would be after an impressive 60 game debut in which he hit .297/.394/.469. A gaudy walk total was the only thing that saved an injury shortened 2013 and when Grandal returned in 2014, he walked and homered often enough to post a .728 OPS despite a .225 batting average. It's all come together in 2015, as his .275/.384/.435 triple-slash results in a 134 wRC+ and .300 TAv, fourth best among regular catchers and the offensive equivalent of Buster Posey. Grandal’s contact rates both in and out of the zone have improved substantially over 2014's numbers but neither is a drastic departure from marks he achieved earlier in his career. There's not much reason to believe the former 12th overall pick will slow down, with a little more power likely to compensate for a little less average moving forward. He hasn't hit much since returning from a concussion on May 30, so that's something to keep an eye but Grandal is a good reminder that you should be patient with young catchers with this kind pedigree.

Brett Lawrie, 2B/3B, Oakland Athletics: -8.92% change

Here's a non-comprehensive list of things Brett Lawrie is good at: striking out (9th worst rate among qualified hitters), not walking (12th worst), antagonizing Royals fans even more than Craig, not hitting all manner of pitch types, and swinging at would-be balls (28th worst). You might look at his chase rate and use it to explain away the deterioration in overall contact rate, but Lawrie is actually making contact on pitches off the plate at the same rate he always has. The real problem has been in the strike zone, where he is both swinging less and making far less contact when he does cut. His 78.57 percent rate in the zone is nearly nine percent off his career average and good for tenth worst in baseball among qualifiers. The overall regression is not just a product of April struggles either. Since May 11 – a month-long stretch during which he's hit .315/.351/.483 – he's swinging a little bit less but making contact at roughly the same poor rate he has all year and is somehow even worse in the strike zone. With Josh Donaldson bringing rain in spite of scorching heat, Lawrie is on the wrong side of a trivia question. His approach isn't likely to remain quite this poor, so some level of rebound is likely but I don't think there's as much upside left to tap as his post-post-hype status might lead you to think. Sell to a believer while he's hot and healthy.

Brad Miller, SS, Seattle Mariners: -7.25% change

Miller is another guy at the bad extreme of the in-the-zone contact leaderboard, as his 77.38 percent rate is eighth worst in baseball. That’s not a death sentence on its own; Miller is surrounded by plenty of valuable hitters but players like Nelson Cruz and Joc Pederson offset their contact issues by hitting the ball a long ways when they do connect. In addition to Miller’s lack of power as a compensating factor, the deviation from his career norm in bothersome. Like Lawrie, Miller’s in-zone contact rate is off almost nine percent from his career average and has decreased considerably from the 90.46 percent mark he posted during his promising rookie season. Miller’s swing rates are also down, dampening the effect of the contact issues on his overall line, which could provide an opportunity to sell. His overall .229/.310/.404 triple-slash isn’t horrid but it is buoyed by a short mid-May power outburst. He’s been atrocious since then. If there’s a shortstop-desperate owner in your league, play up the modest power/speed combo and the prospect of multi-position eligibility down the road before his value completely craters.

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As a Nats fane, the Danny Espinosa saga is torture. He teases and fails, teases and fails, teases and ...

As a fantasy player, I see a guy with 2B, 3B and possibly soon OF eligibility who can potentially help in multiple categories while hopefully not torpedoing your batting average.

The question is, when does this become real enough to pop him. In a 14-team mixed, 40-man-roster dynasty league, he's available. In a 12-team mixed head-to-head redraft 5x5 league, he's available.

But I am always on edge with this guy waiting on the next 3-for-40.

Espinosa should definitely be owned right now in a league with 560 roster spots. Standard 12 team probably depends more on your roster construction and need at 2B/MI.
Nationals had the DH in the last two games, which is the only reason he was in there at 2B. I'm not buying the playing time argument unless he moves to the OF.
@gregwellemeyer: Those 560 roster spots include almost all of the top 100 prospects and some who aren't even in those rankings yet (i.e. many of the first-rounders in this month's MLB entry draft).