Months are nice ways to draw a line in a season and take stock of where you are. It's an arbitrary line, but unless a player gets hurt or makes some kind of notable mechanical adjustment, any endpoint within a season is going to be rather arbitrary. 

One thing you have to guard against, however, is overreacting to the results of any one month of action, especially April. When something happens at the beginning of the season, it's easy to overreact, but sometimes a hot April is just that. Sometimes a hot April turns into a breakout, but it doesn't necessarily have to. 

Let's take a look at the 10 players who have seen the biggest drop in their production from April to May, and whether their hot April or cold May tells us anything about what we should expect moving forward. 

Chase Headley N.Y. Yankees 3B
April wOBA: .389 May wOBA: .188 - Chase Headley was, to put it simply, playing over his head in the first month of the season. That isn't to say that his performance to date in May is more indicative of his true talent level, but it never made sense to expect him to sustain his April performance. Reality is probably somewhere in the middle, with Headley returning to the realm of the barely Fantasy relevant.
Ryan Zimmerman Washington 1B
April wOBA:.551 May wOBA:.355 - So, you're telling me Ryan Zimmerman isn't one of the best hitters of all time? This is a simple case of regression to the mean, and the good news is, Zimmerman's mean really does seem to be a lot higher than it was in recent years. An .833 OPS might be more what we should expect from Zimmerman moving forward, and it is worth noting that Zimmerman's flyball rate has fallen from 40.6 percent to 30.8 percent in the month, actually below where it has been in recent seasons. If you're buying Zimmerman as a star once again due to changes in his batted ball profile, that's a potential red flag.
Khris Davis Oakland LF
April wOBA:.420 May wOBA:.230 - You can't chalk this slump entirely up to bad luck for Davis, but that probably gets you most of the way there. His plate discipline has fallen apart in May, but his strikeout rate has actually only gone up two points, so there isn't a ton lost there. He is still putting the ball in the air a ton, and still has a massive 46.9 percent hard-hit rate in the month, so Davis probably deserves more than just the three homers he has hit so far. Davis is such a proven commodity as a power threat, it seems pretty safe to disregard even a slump this deep.
Eric Thames Milwaukee 1B
April wOBA:.517 May wOBA:.337 - Like Zimmerman, Thames had plenty of regression coming. And like Zimmerman, you can hardly be disappointed by what he has produced even in his regression phase. Despite dealing with a case of strep throat -- among other maladies -- Thames is still striking out at around a league average rate while continuing to show strong plate discipline overall. His power hasn't been quite so Herculean in May, but if this is the low end of Thames' production, he still looks like a star.
Steven Souza Tampa Bay RF
April wOBA:.409 May wOBA:.231 - There were some real promising signs for Steven Souza in April, primarily with his strikeout rate, which he had cut to 25.9 percent. That isn't even close to league average, but it represented a real improvement on his career rate north of 33 percent. Unfortunately, he has regressed in a huge way in May, going down on strikes on a whopping 37.3 percent of his trips to the plate. The skill set has always been there for Souza, but contact issues continue to limit his ability to reach it. It doesn't look like that has changed.
Jose Ramirez Cleveland 3B
April wOBA:.411 May wOBA:.260 - Jose Ramirez looked like he might be taking a big step forward as a power threat in the early going, however after racking up 12 extra-base hits in 24 games in April, he has just three in 17 May games, including no homers. He still has solid plate discipline, and a .227 BABIP explains away at least some of his struggles, but it may be premature to buy in entirely to some new level of power production. For the season as a whole, however, Ramirez does have a career-high flyball rate and hard-hit average, so it's not out of the question. We'll see where things settle in before long.
Bryce Harper Washington RF
April wOBA:.520 May wOBA:.378 - Like Thames or Zimmerman, there was a market correction coming with Bryce Harper. However, whereas his wOBA fell to .333 last May, Harper's regression this season has been much more gradual. He is still hitting for solid power, and if the worst we see from him is an .896 OPS over 15 games, he's going to have another huge season. For reference, Harper's worst month in 2015 saw him post a .909 OPS, so he's not far off that pace.
Yuli Gurriel Houston 1B
April wOBA:.360 May wOBA:.221 - Yuli Gurriel has remained a plus contact hitter, but that's about all he does well after 284 trips to the plate in the majors. That should lead to solid batting average numbers, but he has just a .291 BABIP for the season, and a .279 mark in his career overall. The power just hasn't been there, however, and until that shows up consistently, it seems reasonable to mostly ignore him at this point.
April wOBA:.415 May wOBA:.276 - As with Ramirez, the question is how much of Francisco Lindor's early-season power increase will stick. He has increased his flyball rate from 28.4 to 44.9 percent, and has also seen his hard-hit rate jump to 33.8 percent, the highest of his career. The hard-hit rate hasn't sustained into May, but his changed batted-ball distribution has kept up, which is a positive sign. Lindor has gone on record as saying he isn't trying to change his swing, so it's interesting that the flyball rate has remained the same. That might be a sign that his power might be here to stay, though it's fair to wonder if he has enough raw power to succeed as a flyball-heavy hitter.
Joe Panik San Francisco 2B
April wOBA:.340 May wOBA:.203 - Joe Panik was a popular bounce-back candidate after he had just a .245 BABIP last season, but that was based on the assumption that he was continue to be a decent power threat while also walking more often than he struck out. He has regressed in nearly every way possible to this point, making it hard to get excited about a potential bounceback.