There are slow starts, the kind you can hand-wave away because it's only April 16 and we're talking about a few dozen plate appearances ... and then there are actual slow starts.

Knowing the difference between them is important, because you want to know if a rough early season line is because well-struck balls aren't finding holes, or if it's because a player is performing poorly and deserves every bit of that rough line. It matters, a lot.

For example: Brandon Drury is hitting .140/.183/.211, and that makes sense, because he's struck out in over 40 percent of his plate appearances. His Statcast expected average, based on the usual outcomes of his exit velocities and launch angles, plus his strikeouts and walks, is .163. He's mostly earned that line. On the other hand, Jesse Winker, hitting a mere .186, has an expected average of .288. You be tempted to look at these two 'slow starts' similarly. You shouldn't. They got there differently.

So, let's try to figure out the difference. Let's look at 10 hitters (minimum 30 plate appearances) who have the biggest gap between their actual performance, expressed in Weighted On-Base Average (or wOBA; it's an OPS-like metric, where the Major League average is .320) and their expected performance, expressed in expected Weighted On-Base Average, which gives credit for the quality and amount of contact, regardless of opposing defense or ballpark effects.

Allow us to be clear here: This is not a list of hitters who can entirely claim 'bad luck,' though that may be true in some cases, and it's not a guarantee that these hitters will improve their lines going forward. This is more about explaining what has happened than what will happen, and that's valuable, because knowing how you got to this point is valuable. Players are listed in order of their gap between their wOBA and xwOBA, starting with the largest.

1) Franmil Reyes, Padres

Actual: .222 AVG., .533 SLG, .345 wOBA
Expected: .357 AVG, .819 SLG, .499 wOBA

This is already happening, for what it's worth. Reyes has six hits and three home runs in his last five games, including a crushed opposite-field homer on Monday night. He was hitting all of .143/.235/.286 as recently as April 10. He's already got a 119 OPS+, meaning he's nearly 20 percent better than league average despite that relatively meaningless .222 batting average.

It's not because of strikeouts, because his 14.3 percent strikeout rate is considerably better than the Major League average of 23.4 percent. It's not because of soft contact; his 44.4 percent hard-hit rate is above the Major League average of 37.1. Sometimes there's not a reason this early, at least not a satisfying one.

For example: Here's a Reyes fly ball hit at 106.7 MPH on the opening week of the season, a 393-foot shot that pushed San Francisco outfielder Steven Duggar to the deepest part of the warning track. Look at how often balls entering 2019 hit that hard, at that launch angle, turn into homers. It's "almost all the time."

Entering the season, Reyes was one of the more highly-anticipated young Padres hitters, based on what he did at the end of 2018. Based on what he's doing so far -- the amount of contact and the quality of it -- he's been one of the seven best hitters in the game, behind names like Mike Trout, Cody Bellinger, and Anthony Rendon. He has nine outs hit at 100 MPH or harder, seventh-most in baseball. There's a lot more here than you've seen. You're starting to see it.

2) Jordy Mercer, Tigers

Actual: .233 AVG, .326 slugging, .278 wOBA
Expected: .313 AVG, .604 slugging, .413 wOBA

Mercer has never been known for his bat, having hit just .255/.316/.382 over his career, but he's earned better than this. In fact, he's off to a pretty red-hot start in the early going, hitting the ball hard -- his hard-hit rate of 43.8 percent is a huge jump over his 31.2 percent last year -- and he's hitting fewer ground balls than ever. Those are both good things.

That the production hasn't been there is in part due to an increased strikeout rate, as he's whiffing at a career-high 23.4 percent mark, a huge number for a contact hitter who struck out just 15 percent of the time as recently as 2017. Mercer turns 33 in July, and he's currently sidelined with a quad strain, so it's not likely he's suddenly undergoing a Daniel Murphy-esque conversion into a power hitter. (Although if he does, you heard it here first.)

That said, it does seem like he's trying something different, trading contact for power. That makes him one to watch when he returns to the active roster.

3) Chris Davis, Orioles

Actual: .089 AVG, .200 slugging, .177 wOBA
Expected: .190 AVG, .411 slugging, .294 wOBA

Yes, that Chris Davis, the one who finally snapped his record-setting hitless streak on Saturday, then hit his first homer of the year on Monday in Boston. As those expected numbers show you, this isn't really about a strong hitter having an unfortunate start, because even if he did have the .190 average and .411 slugging his production might indicate, those are still disappointing numbers.

In this case, it's been a rough April all around, though it's worth noting that it's getting better. Over the last week, Davis has had an expected average of .309 and an expected slugging of .660. His real numbers are never going to catch up to that, but at least it's progress. It's just that -- before Saturday anyway -- the shocking lack of any dribbler or bloop or line drive finding anything but gloves just made it look slightly more rough than it needed to be.

4) Josh Harrison, Tigers

Actual: .135 AVG, .154 slugging, .181 wOBA
Expected: .224 AVG, .360 slugging, .291 wOBA

Harrison is barely off to a better start than Davis, with just a single extra-base hit, a double, so this is also a case of "weak underlying numbers, plus under-performance on top of it." Harrison is striking out (20.3 percent) a little more than he did with Pittsburgh, though his hard-hit rate and walk rates are each up slightly.

Part of the culprit may be his new home park, because his highest-value out of the season was this 412-ft blast that would have been a home run in nearly any other park.

So he might wish he'd hit that one somewhere else, but for the most part, there's not a deeper story here. Harrison is off to a very disappointing start for Detroit -- and it's not just about bad fortune.

5) J.D. Davis, Mets

Actual: .263 AVG, .553 slugging, .408 wOBA
Expected: .387 AVG, .743 slugging, .517 wOBA

When the Mets traded for Davis from Houston in January, it was partially about his ability to play multiple positions, and partially about the expected thunder in his bat -- he'd caught our eye in 2017 with an elite hard-hit skill on balls in the air. So far, so good: Davis is off to a pretty massive start in his first 47 plate appearances, with three home runs and a 159 OPS+. He's got more walks (nine) than strikeouts (eight); he ranks fourth on the hard-hit leaderboard.

This is everything the Mets hoped for and more. If there's an issue here, it's that 75 percent of his hard-hit balls have been grounders, which generally become outs. But that's a minor issue, for now. Davis has been spectacular, even if he 'deserves more.'

6) Jesus Aguilar, Brewers

Actual: .152 AVG, .196 slugging, .226 wOBA
Expected: .247 AVG, .413 slugging, .334 wOBA

Last year, Aguilar had something of a breakout year, following up on a successful 2017 as a part-time player with a massive 35 homer, .274/.352/.539 season. This year has been a struggle, as Aguilar is still hunting for his first home run.

Interestingly, he's making far more contact this year, cutting his strikeout rate from 25.3 percent to 15.8 percent. But the problem is that he's making worse contact too, because his hard-hit rate has dropped from a strong 42.6 percent to a weak 31.6 percent. (That's why his expected numbers are down so much from last year's excellent numbers.)

So there's that, but he's also under-performing even his modest expected numbers. We looked at all of his hard-hit (so 95 MPH or higher) outs, and for the most part, they've been hit right at someone, like this 103.6 MPH rocket that somehow turned into a double play. That part of it, at least, Aguilar can hope his fortune will change -- but this doesn't explain the hard-hit drop. Perhaps it was better to whiff more, if it meant crushing more.

7) Kendrys Morales, A's

Actual: .214 AVG, .286 slugging, .285 wOBA
Expected: .282 AVG, .511 slugging, .392 wOBA

Morales is famous for under-performing his expected stats. He does it every year. In fact, only one hitter between 2016-'19 (with at least 750 plate appearances) under-performed by as much, and Miguel Cabrera is a somewhat similar slow-footed slugger.

That shouldn't surprise, and this is more of the same. Morales, again, has an elite hard-hit skill, with his 55.9 percent ranking in the 94th percentile. He'll do better than this, because it's always good to hit the ball hard, and you won't have a .286 slugging long like this. But he's going to underperform. He's slow, and he's shifted constantly. It's nearly a given at this point.

8) Gary Sanchez, Yankees

Actual: .268 AVG, .732 slugging, .439 wOBA
Expected: .346 AVG, .930 slugging, .544 wOBA

See: Davis. Sanchez, currently on the injured list with a calf strain, has been destroying the ball, with a 50 percent hard-hit rate and a 20 percent strikeout rate that's down from last year's 25 percent. That his underlying stats suggest even more tell you something about just how hard he's been smashing. This is not saying he's likely to slug .930 for the rest of the season (he's not), but it is a good window into just how good his start has been.

It's also an enjoyable turnaround from last season. In 2018, you might remember, Sanchez had the second-lowest Batting Average on Balls In Play (.197) of the 21st century, at least among those with as many plate appearances as he had. This year, it's actually worse.

9) JD Martinez, Red Sox

Actual: .344 AVG, .563 slugging, .412 wOBA
Expected: .388 AVG, .795 slugging, .515 wOBA

Speaking of a hitter off to a great start who somehow may have deserved more: This feels unfair. Martinez isn't having a slow start. He's having a fantastic one. After extending his hitting streak with a double in Monday's loss to Baltimore, Martinez is hitting .344 with a .412 wOBA, which is each outstanding numbers.

It's not enough. His expected average of .388 is third, behind Bellinger and Trout. His expected slugging of .795 is sixth. His expected wOBA of .515 is also sixth. He's off to a good start, but the underlying skills say he's off to a great start.

Just look at this out, hit 410 feet to the absolute deepest part of Fenway.

And look at this out, hit to basically the same 'deepest part of Fenway' spot. Those are home runs in nearly any other park. Here, they're outs. This isn't a 'slow start,' because Martinez is already raking. It's just not as good as it could be. Which is a terrifying thought.

10) Joey Gallo, Rangers

Actual: .217 AVG, .587 slugging, .396 wOBA
Expected: .312 AVG, .758 slugging, .491 wOBA

Remember: Batting average usually doesn't matter, and it definitely doesn't for a hitter like Gallo. Despite the .217 average, he's got a 140 OPS+, thanks in part to a more patient approach. (His walk rate is up from 12.8 percent to 17.9 percent.) And, as Gallo always does, he's hitting the ball hard, though even for him, 2019 is something special -- his 66.7 percent rate is second-best in the game, and up by a lot from last year's 49.1 percent mark.

You may have also seen what he did on Monday night.

So there's a lot to like about Gallo's season as it is, but there's something of problem here. In 2017, Gallo hit 27.9 percent of his balls on the ground. In 2018, he hit 29.6 percent on the ground. So far in 2019? That's 44.5 percent. Even for someone who hits as hard as he does, that's far too much, because a crushed ball on the dirt isn't going to land in the seats. Either way, Gallo is off to a strong start, regardless of what his batting average says.