RotoBaller's Nick Mariano looks at some fantasy baseball bats for week twenty that are hitting either extremely hot or cold in the power department.

Welcome back to this investigative piece where we examine players who have seen some notable changes in their power profiles -- for better or for worse -- in 2017.

As usual, you don’t need me to tell you that Miguel Sano or Aaron Judge is strong or that Jarrod Dyson and Billy Hamilton are toward the bottom in average exit velocity. We’re approaching the stretch run of the regular season and that means making some bold moves on the waiver wire and some tough calls when it comes to addressing cold streaks.

Identifying top power risers and fallers for each week can help you spot the best pickups before your competition. We'll do the hard work for you, looking at the underlying metrics that influence a hitter's power: fly-ball, pull, hard-hit rates and exit velocity.  Consider buying these week 20 power risers and selling these week 20 power fallers.

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Power Risers

Eddie Rosario - (MIN, OF):

While he didn’t go deep in Thursday’s doubleheader, Rosario had launched five long balls alongside four doubles in his previous nine games with 12 runs scored and 10 RBIs. Heck, he even swiped a base in there. And it isn’t like he was bad during the doubleheader -- going 3-for-9 combined -- but many will remain skeptical of the 25-year-old. Questioning this surge is both understandable and wise, but do not that this a guy who hit 16 homers combined between the Majors and Minors in 2015 before slugging 17 combined HRs in ’16.

So, now the year is 2017 and Rosario has suddenly turned it on in August. How much are we really buying in here? Comparing his August to July, his fly-ball rate is up 12 percentage points to 47.6 percent with a healthy 18-percentage-point jump in his pull rate to 54.8 percent. Of course, we’re suckers for exit velocity most of all and Rosario doesn’t disappoint, with a 43 percent hard-hit rate and paltry 9.5 percent soft-contact rate thus far. Heck, when he went 3-for-4 with two homers on Aug. 8, all four of the balls he hit into play clocked in at 102.7 mph or faster (including the out he made). He isn’t the next Giancarlo Stanton, but he’s got more pop than you think and is right at the age where the prime form can be found.

C.J. Cron - (LAA, 1B):

Cron has always been a maddening fantasy asset to own because he always seems to get hurt after starting a hot streak. We’ll try to knock on as much wood as we can here because the 27-year-old is hitting .324 since the All-Star break (.340 in August) with seven round-trippers, 18 RBIs and a 1.016 OPS. His hard-hit rate is up over 10 percentage points with his usual fly-ball rate of roughly 48 percent and a lofty 55 percent pull rate.

Not only has Cron bashed 15 balls into play at over 100 mph this month, but six of those have been at over 110 mph -- and none of those six have had a negative launch angle. He’s got the swing to wreck baseballs and has a career .185 ISO despite all of his streaks and the injury-marred at-bats of his past. Don’t throw your wallet at the screen for him, but if you’re debating whether to make the add or not, you probably should.

Zack Cozart - (CIN, SS):

Cozart has a career-high 17 homers this season with an impressive .312 batting average that hasn’t fallen off in the second half. Yes, after hitting just .223 after the All-Star break last season, the 32-year-old is turning in a .300 clip thus far with eight long balls in just 70 ABs after clearing the fence nine times in 247 first-half ABs. Not bad at all.

We can’t expect him to hit fly balls at an insane 64 percent clip the rest of the way, but his pull rate of 59 percent isn’t far off from his norm (52 percent in July), with those first two metrics carrying an average 32.4 percent hard-hit rate for August. Plenty of people seem to be worrying about another dropoff like last season, but my stance is that you only have to worry about durability with Mr. Zack. Outside of that, the performance should be there.

Power Fallers

Jackie Bradley Jr. - (BOS, OF):

I relish nearly every opportunity I get to shine light on JBJ, as I think everyone hitches their wagons way too closely to those few hot streaks that elevated him toward the top 100 draft picks heading into 2017 drafts. It shouldn’t come as any surprise to his owners that he’s hitting just .198 with one measly round-tripper since the All-Star break (31 games). That homer came off of James Shields, so I don’t even know if we can count it. He’s also seen his strikeout rate spike to 31 percent after whiffing at a 19.9 percent clip in the first half. So the real question is, “how bad is it, Doc?”

Bad.

Because his hard-hit rate has dropped to 22 percent in August. Because his pull rate has done the exact same thing. Because he’s only hitting fly balls on one of every four batted balls this month. His soft-contact rate is up five percentage points in the second half. Only two of his last 20 batted balls have been struck at over 100 mph, and both of those had negative launch angles. It’s justifiably ugly right now. You can continue hoping for a rebound, but he’s cuttable in nearly all formats.

Brett Gardner - (NYY, OF):

Gardner hit a double on Thursday. It was pretty cool. It was also just his second extra-base hit in 61 August at-bats. I realize that Gardy is a slap-happy hitter who gets to bat leadoff and enjoy the short porch of Yankee Stadium, but there has to be a line drawn somewhere. The guy made do with a poor 23.6 percent hard-hit rate in July and we stomached it, but that mark has fallen to 14 percent in August. That’s the seventh-worst mark out of all qualified hitters! Names worse than him include Jarrod Dyson, Dee Gordon and Billy Hamilton -- in other words, the “No $&#^, Sherlock” group of zero-power hitters.

We love that Gardner can steal bases, but he won’t steal enough to offset being a total dud in the power department like those other guys. Banking on the raw potential of his hitting environment is fine if you have the room to bench him, but those of you whose trade deadlines haven’t passed can probably still fetch a pretty penny for him based on his overall numbers and the whole “Yankees allure” thing. He’s topped 100 mph on a batted ball just twice this month, and both were singles because there was no lift. This is the time of the season where patience can pay off if you have flexibility, but also bounce you out of contention if you’re stubborn about it.

Mike Zunino - (SEA, C):

But Zunino has two homers in his last six games! Okay, I don’t actually think there’s going to be any push back on this because most of you are rational and can do basic arithmetic. He’s just 7-for-39 (.179) in 13 August contests thus far with a gross 34.8 percent soft-contact rate (21.7 percent hard-hit rate) that has sucked all of the life out of a 39 percent fly-ball rate and 48 percent pull rate. There’s no doubting that his muscle can send a baseball far when he connects, but his timing is verifiably off right now.

What’s interesting is that he’s actually making significantly more raw contact in August than he did in July -- with a 67.8 percent contact rate compared to 56.3 percent in July -- and has brought his swinging-strike rate down from 23 percent to 15.8 percent. This goes with a zone-swing rate of 68 percent compared to 77 percent in July. So, he’s more selective and it’s paying off with some increased plate discipline, yet when he does swing, it’s just not doing nearly as much. He either needs to strike a different balance or get back to his old, more aggressive, ways. This won’t cut it.

More Risers and Fallers