At the bottom of the Fangraphs’ leaderboard for wOBA over the last 30 days is Carlos Gonzalez at .227. He’s 10 points lower than anyone else, and he only has two RBI over the past month. CarGo’s numbers are well off of last year’s 40-homer season, and he’s been, according to Fangraphs, a negative on offense, defense and the bases this year, totaling 0.0 WAR. I usually look at a player’s walk, strikeout and BABIP rates to begin determining why he’s struggling or excelling, but when digging into CarGo’s numbers his performance in plate discipline over the last month is fairly close to his career performance.

What stands out is his .256 BABIP. Now you might think as soon as that regresses to normal he’ll be fine, because every other season he’s been at .283 or above. But this isn’t a case of some bad batted ball luck. CarGo is hitting virtually a career-low in fly balls, at 29.6 percent, well below his career 35 percent rate. At Coors, you’d like to hit the ball in the air, but Gonzalez has expanded his zone this year. He’s swinging at a career-worst 44 percent of pitches outside the zone, and making contact 60 percent of the time – almost a career-“high.” Swinging at pitches outside the zone leads to weaker contact, so even though he’s not striking out a ton he’s hitting the ball very weakly. That explains his career-worst 16 percent infield fly ball rate and 49 percent ground ball rate. Gonzalez’s exit velocity has been below league-average for four of seven weeks this year, mostly because 25 percent of pitches he’s seen have been outside the zone, low and away. Until he starts taking more pitches outside the zone he’s going to keep struggling with his power output.

Coming in at ninth in wOBA in the last month is Joc Pederson. The 24-year-old is hitting .235/.391/.574 with a 20 percent walk rate and six home runs. Even with his second-half slump last year he still put up a .335 wOBA. This year, he has the same walk rate (15 percent) and strikeout rate (29 percent), but he’s hitting for more power (.206 isolated power in ’15, up to .278 this year). He’s always going to swing and miss, but he’s also always shown a good eye at the plate and prodigious power. According to Statcast, Pederson ranks 12th in average exit velocity this season. That has all led to wOBA that’s .383, which ranks 13th among outfielders.

It looks like Pederson may have shortened his swing a little bit, as he’s reduced his swinging strike rate from 14 percent last year to under 12 percent this year, and he’s chasing less often at pitches low and outside the zone. Pederson hit 26 home runs last year at age 23, and he’s on his way to matching that number this year. Even though he strikes out a lot, this type of power is uncommon.

Leonys Martin doesn’t rank in the top 30 in wOBA in the past month, but the former Ranger is playing well for Seattle. He has eight home runs and seven steals, and his .238 isolated power ranks 24th among outfielders in the last month. What sticks out like a sore thumb is his 21 percent home run to fly ball rate, which is almost triple his career rate. But he is hitting 45 percent of balls in play as fly balls, which is much higher than his 30 percent career fly ball rate. Now, he probably won’t continue to hit six home runs a month, but with a new focus on lifting the ball Martin can now provide some power with his legs – he averages 31 steals per 162 games in his career.

Austin Jackson has zero home runs and stolen bases over the past month. He only has one steal on the season, and he’s still looking for his first homer. He’s been hitting near the bottom of the White Sox lineup most of the season, and with his .282 OBP there’s no reason for him to be moved up the top of the order to try to “get him going.” Jackson always relied on a high average on balls in play to produce, but so far this year he has a career low BABIP of .287, which is continuing a disturbing trend for someone who relied on it so much. Jackson has three double-digit home run seasons, but none since 2013. You’d think with his wheels he’d be able to rack up some triples, but he only has one so far, and his triples totals have declined each year since 2011. His isolated power is also at a career-low after a one-year spike last year stopped another trend going the wrong way. If Jackson’s not going to give you a high average thanks to a good BABIP and he’s not stealing bases he’s worthless to roster at this point.