This story was excerpted from Alex Stumpf’s Pirates Beat newsletter. To read the full newsletter, click here. And subscribe to get it regularly in your inbox.

So much of baseball is centered around what you can do against the fastball. If you can hit it, you have an offensive foundation. If you’re a pitcher and can make hitters miss it, you have a very valuable tool.

And when looking at some of the hottest and coldest Pirate performers in the second half of this year, it also starts with the fastball.

Fastball success: Joey Bart
Bart has been the most pleasant surprise on the offensive side of the ball this year, going from being in DFA limbo with the Giants to someone the Pirates want to hang onto. His bat is a major reason why.

Sure, there is probably some small sample size in play, but Bart is hitting .308 with a .585 slugging percentage against fastballs this year. Against just four-seamers, his +9 run value is in the top 20 of all hitters, and when prorated for 100 pitches, he has the best run value of any hitter in the game (min. 25 PAs). Not to mention all four of his extra-base hits since the All-Star break are off of fastballs (two doubles off four-seamers, two homers off sinkers).

As a bonus, he’s hitting other offerings too. Four of his last six hits are off breaking or offspeed pitches, and he had just five hits off those types of pitches in 2023.

Fastball struggles: Ke’Bryan Hayes
Hayes certainly has the potential to be a plus hitter – we saw it across the second half of last season – but it’s looking less likely that he’s going to reach that level of production this year. His .585 OPS is the lowest among hitters who qualify for the batting title, and he’s in the bottom one percent of batting run value (-18).

A year ago, he hit .302 against the fastball with a .466 slugging percentage. This season, that slug has been cut in half to .228. If that doesn’t improve, it would be the worst slugging percentage against fastballs of any hitter in the pitch tracking era (min. 200 PAs). His average exit velocity against the pitch has also dropped dramatically (95 mph to 89.5 mph).

Since the All-Star break, he’s hitting .200 (7-for-35) against fastballs with no extra-base hits while grounding into four double plays. There’s a good hitter in there, but Hayes has looked lost at the plate.

Fastball success: Aroldis Chapman
Chapman has been streaky this season, but when he’s clicking, he’s as dominant as ever. A lot of that comes down to throwing his pitches in the strike zone, and surprisingly, no Pirate has done that better in the second half than Chapman. Since the break, 66% of his pitches have been in the strike zone, compared to 48.6% in the first half.

Chapman has leaned on his four-seamer more of late after opting for more sinkers across May and June. The results with the four-seamer have been great, holding hitters to just two singles and three walks over 22 plate appearances since the start of July. In that time, he’s upped his four-seamer usage to 41.2% and his sinker has dropped to 22.2%. His sinker has intriguing peripherals, but if it’s just about throwing pitches in the zone, the four-seam is the better call. This year, 56.4% of his four-seamers have landed in the Gameday strike zone, compared to 46.9% of his sinkers.

Fastball struggles: Colin Holderman
It’s been a rough week for Holderman, who was twice beat on fastballs over the past week for deciding home runs. He tried to get by leaning on his cutter in his last outing Sunday, but eventually turned to the four-seamer, which Joc Pederson hit to left for a three-run shot. The thing is that was a 100 mph pitch and not in a bad spot. He just got beat, which is why he and the Pirates aren’t pushing the panic button.

"I think just keep going at it,” Holderman said. “I've been executing the game plan, executing my pitches. Sooner or later, it's going to get that one zero and we're off to the races again. It's just finding that next zero."