It didn’t take long for Ken Giles to make a name for himself, despite coming up as “just” a set-up man on a relatively bad Philadelphia Phillies team. In his debut season in 2014, Giles struck out 64 batters in 45.2 innings and posted a minuscule 1.18 ERA and 1.34 FIP as a 23-year old. Last year, Giles followed up his stellar freshman season with an equally impressive sophomore campaign, fanning 87 batters in 70.0 innings of work, notching a 1.80 ERA and 2.13 FIP. After a trade-deadline deal sent incumbent closer Jonathan Papelbon to the Washington Nationals, Giles officially took over the closer role in Philadelphia and finished the year with 15 saves, all coming after July 28.

After those two fantastic seasons in the back end of Philadelphia’s bullpen, the rebuilding Phillies decided that their young relief ace was more valuable to them as a trade chip than a current player, and on December 12, 2015 Giles was traded (along with a low-level prospect) to the Houston Astros for a quintet of players, including former No. 1 overall draft pick Mark Appel and young right-hander Vince Velasquez.

Giles’ role with his new club was not immediately obvious, but many speculated he would be the team’s closer heading into spring training. The club, however, kept quiet on the matter, further fueling public debate over Giles’ best fit on the team. On April 4, Astros manager AJ Hinch announced that club veteran Luke Gregerson would begin the season as the team’s closer. This displeased some — despite Gregerson’s success within the role in 2015 — due to the seemingly steep price the club paid to acquire Giles.

Hinch’s decision was validated almost immediately, as Giles’ season began about as poorly as one could’ve imagined. In 115.2 innings pitched between 2014 and 2015 in Philadelphia, Giles allowed just three home runs — a number he matched in less than four innings with the Astros, as he allowed longballs in three of his first four outings with Houston. Through April, Giles had allowed 10 earned runs in 10 innings. However, his peripheral numbers were not awful, as he struck out 14 batters and walked just four, giving him an xFIP of 3.23 despite the 6.75 FIP and 9.00 ERA. Giles’ HR/FB rate was an astounding 40 percent, compared to the league average of 11.8 percent over the season’s first month.

May was a slight improvement for Giles, as he went the entire month without allowing a home run and continued to strike out batters at a good rate. Over 11.1 innings, he fanned 14 batters and walked five while allowing five earned runs. For the month, he accumulated a 3.97 ERA, 2.00 FIP, and 3.93 xFIP. At the end of May, Giles had pitched 21.1 innings with a 28:9 K:BB ratio, and had a 6.33 ERA, 4.23 FIP, and 3.60 xFIP. Perhaps the most troubling statistic, however, was Giles’ ground-ball rate, which sat at just 31.1 percent after his first two months. Over his first two seasons, Giles’ ground ball rate was much higher, at 44.6 percent. Giles’ strand rate was also nearly 78 percent in his time with Philadelphia, but stood at just 66.9 percent over April and May of 2016.

While May was an improvement over April, Giles was still not nearly as effective as he was in his stint with the Phillies. June was a bigger step in the right direction, though, and Giles once again brought down his monthly ERA to 2.31. He allowed three earned runs in 11.2 innings of work, striking out 14 and walking just two. That month, his FIP and xFIP were both around 2.50 and his strand rate and ground-ball rate increased to 88.2 and 38.7 percent respectively.

July went even better than Giles could’ve hoped, as he allowed just three hits and no runs over 8.2 innings, striking out an astounding 18 batters while walking just two. Once again, his strand rate and ground-ball rate increased, posting 100 percent and 45.5 percent marks, respectively. For the month, his FIP was actually negative, at -0.31. August has gone well for Giles, too, as he’s struck out 21 batters against two walks in 10.2 innings (through 8/30). The long ball has hurt him a bit — solo homers accounting for two of the three earned runs allowed in the month — but his ERA for the month sits at 2.53 ERA, and he owns a 2.49 FIP. His strand rate in August sits at 88.2 percent, and his ground-ball rate has gone up again to 52.4 percent. On August 7, Giles even had a game in which he struck out six batters in just 1.2 innings.

Since the beginning of June, Giles’ numbers are eye-popping, especially when compared to his numbers through May:

Giles is a pitcher who relies heavily on his “stuff” to get outs. He throws just two pitches — fastball and slider — so getting hitters to guess on a wide variety of pitches isn’t his game. However, both his fastball and slider are excellent offerings, which gives him the ability to succeed despite a limited arsenal. When working with just two pitches, location is important to keep hitters off-balance. In the first two months of the season, Giles’ location was his issue — the velocity and movement on both pitches has been comparable throughout the season — as you can see from the heat maps of his pitches through May:

Fastball:

Slider:

The fastball seemed to be erratic, with no one area particularly heavily-worked compared to others. The highest-concentrated area was inside to right-handers, which is an area that allows batters to hit to the pull field, where the most damage is done. His slider was also left close to the zone most of the time, which limited his ability to generate swings and misses on the pitch. Since the beginning of June, however, Giles has improved his command considerably, as evidenced by the second set of heat maps from June-August:

Fastball:

Slider:

Giles’ fastball is more consistently located closer to the middle of the zone and towards the lower half, which not only allows him to force batters to swing at the pitch but keeps them from turning on balls and doing damage to the pull field. His slider heat map is almost identical to the one from April and May, but shifted lower by almost a foot. Instead of working from the middle of the zone to the bottom, he’s now working the slider from the bottom of the zone to down below the knees. This has given Giles the ability to not only get more whiffs on balls out of the zone, but to generate more ground balls with the pitch. The fact that the fastball and slider locations are more similar also likely gives Giles an advantage, as he can play the slider off of the fastball or vise versa.

Giles has also — perhaps even more importantly — changed his usage patterns since the end of May. He’s not only used the slider much more, and more effectively, but he’s also changed when he uses the slider, particularly to right-handed hitters. Compare Giles’ usage charts from the first and second “halves” of his season:

April-May:

June-August:

As you can see, Giles has begun to pitch to right-handed batters the same way he has pitched to left-handers this year. All season, Giles has used his fastball heavily to begin at-bats against lefties, and even more so when behind in the count. However, to righties — the majority of the batters he’s faced — he’d more or less mixed the two pitches equally in all situations. Yet, since the start of June, Giles has leaned more towards using the slider when ahead of righties and with two strikes. The adjustment has worked to perfection, as Giles has allowed just a .083 batting average and .167 slugging percentage to righties on the slider since June 1.

Thanks to both of the major adjustments he’s made, Ken Giles has been able to reclaim what looked in May to be a down year. Due to other struggles in the Houston bullpen, he’s even taken over the closer role, recording saves in four of his last five appearances. With the Astros desperately needing to make a push for the playoffs in the season’s final month — they enter play on August 30 two games behind Baltimore for the second American League Wild Card spot — Giles is the type of power reliever that could help the team’s playoff chances immensely down the stretch. If Giles could be the difference between winning and losing just a game or two in September, he could be the difference between the Astros making and missing the playoffs. With the way he’s been performing lately, there’s no reason to doubt that he will be a dominant closer down the stretch for Houston.