The Astros' secret weapon

Last month, the Houston Astros missed out on an attempt to bolster their pitching staff at the July trade deadline. They were supposedly in on Jose Quintana, Sonny Gray, Yu Darvish, and Zach Britton but whiffed on all four of them. Some — even the Astros’ own Dallas Keuchel — would say that the team’s front office didn't do enough to shore up their pitching staff.

Others would argue their staff didn't need reinforcements, and that argument starts with the breakout season of Brad Peacock.

Prior to this season, Peacock had a career ERA of 4.57, and an even worse FIP of 4.93. He was plagued by the home run (1.4 home runs per nine innings), and the walk (4.4 per nine innings), while not nearly striking out enough batters to make up for that.

This year, his ERA is down to 3.21, along with an even better 2.66 FIP. He is having success by suppressing home runs and enjoying a huge uptick in strikeouts. He has allowed just five home runs in 98 innings pitched (0.46 HR/9), despite calling Minute Maid Park, one of the most hitter friendly parks in the league, his home. His 0.46 HR/9 is best in baseball among those with over 90 innings pitched.

The Astros should be buying

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Houston was quiet at the non-waiver deadline, but they can right their wrongs by making an August addition.

He's also become one of the top strikeout pitchers in the league. His 11.85 strikeouts per nine innings is fifth-best in the league among those with over 90 innings pitched, behind Chris Sale, Danny Salazar, Max Scherzer, and Corey Kluber. Batters are making contact with his pitches just 71.8 percent of the time, which is tied with Chris Archer for eighth-best in the league.

Despite having thrown fewer innings than Keuchel, Lance McCullers, and Charlie Morton, Peacock has been the Astros’ most valuable pitcher at 2.9 wins above replacement according to FanGraphs. He is the 21st-best pitcher in the league according to WAR, and just one of the 20 pitchers ahead of him has fewer innings pitched (Craig Kimbrel).

Peacock's emergence as a 29-year-old is is due to an overhauled pitch arsenal. Prior to this season, Peacock relied heavily on his four-seam fastball, throwing it over 50 percent of the time in each of his major-league seasons. He complemented his fastball with a curveball, slider, and changeup, without any of three being thrown above 18 percent of the time prior to 2016.

This year, Peacock has added a sinker and has began to utilize his slider much more.

His new sinker, which he throws about a mile per hour slower than his 93 mph fastball, has added another hard pitch for batters to prepare for. Rather than throwing his four-seam fastball over 50 percent of the time, he has thrown it just above 30 percent of the time this year, mixing in the sinker about 20 percent of the time. As a result, batters are slugging just .218 and .418 against his four-seamer and sinker, respectively.

Peacock has also began to trust the sinker more and more as this season has progressed. In May, he threw the pitch just 6.55 percent of the time. So far in August, he has thrown it 32.86 percent of the time, while throwing his four-seamer just 16 percent of the time.

He is also throwing his slider more and more. He has thrown it about 37 percent of the time this year but he has thrown it more often as each month passes.

According to FanGraphs, Peacock throws his slider the fourth-most often in the league among those with over 90 innings pitched.

Not only is he throwing the slider a ton, it's become perhaps his most dominant pitch. Batters are slugging just .306 against the pitch and swinging and missing 22.2 percent of the time he throws the pitch. According to FanGraphs, his slider has been the 19th-most valuable in the league this year.

Peacock is showing no signs of slowing down. The only thing standing in his way is the injuries that plagued him earlier in his career. If he and the rest of the Astros' rotation can stay healthy (granted, a big if), there is no reason a Keuchel-McCullers-Peacock-Morton playoff rotation can't carry this team to the World Series.

Dylan Svoboda is a writer for Beyond The Box Score and BP Milwaukee. You can follow him on Twitter at @svodylan.