Analyzing Ken Giles' Impact on the Astros' Bullpen

Houston finally got a fireballer for the bullpen, something desperately needed.

Look out, the rest of American League. Houston got themselves a closer.

In a trade with the Philadelphia Phillies that took a few twists and turns, the Astros acquired young fireballer Ken Giles and a 17-year-old infield prospect for five players, including starting pitchers Vincent Velasquez and former number-one overall pick Mark Appel.

And as a result, the Astros got themselves a young, fireballing closer capable of missing bats, the likes of which the team did not have during their playoff run in 2015.

In his two Major League seasons, Giles has been nothing short of terrific.

2014 3 1 1 45.2 12.61 2.17 1.18 1.34 1.7
2015 6 3 15 70.0 11.19 3.21 1.80 2.13 2.0

After taking over the closer's role following the Jonathan Papelbon trade to Washington on July 28, Giles went 15-for-17 in save opportunities, posting a 1.71 ERA with 11.28 strikeouts per nine (K/9) and 1.71 walks per nine innings (BB/9). His average velocity dipped a bit in 2015, from 97.2 miles per hour in '14 to 95.6 miles per hour last year, but most of that was due to an early-season drop of about 3 to 4 miles per hour. Later in the season, is was back up to normal, with Giles hitting triple-digits on numerous occasions.

Compare that to last season's closer for the Astros Luke Gregerson, who had a solid season, going 31-for-36 in save opportunities, with a 7-3 record, a 3.10 ERA and a 2.86 FIP. However, he did much of that thanks to a career-high ground ball-to-fly ball rate of 2.61, far higher than his career average of 1.57. Last year, he got 60.4% of batters to hit the ball on the ground. His previous high was 52.2%, done in 2014.

Houston was clearly looking for a ninth inning guy who could miss bats, and Giles certainly does that better than Gregerson. 

Player K/9 K% BB/9 BB%
Ken Giles 11.19 29.2 3.21 8.4
Luke Gregerson 8.7 24.7 1.48 4.2

Those numbers are for 2015 and show that, while Gregerson walked fewer batters, Giles was far better at getting batters to swing and miss. Gregerson has always done well with batting average on balls in play (BABIP), a career .267 average and a .264 average last year, which means it's something that can now largely be expected by Houston. But there is more risk in relying on a soft-tossing ground-ball pitcher to be your closer than a pitcher like Giles, who put up huge numbers last year despite a higher-than-league-average BABIP of .311

Not only that, but Giles is just 25 and has already put together two of the best seasons a relief pitcher has ever had.

That is not hyperbole. That's just fact.

In short, Giles was desperately needed by the Astros.

As a team, their relievers averaged 90.9 miles per hour in 2015, dead last in all of baseball (next closest was the Angels at 91.3). Last season, there was only one pitch thrown by a Houston Astro that traveled 99 miles per hour or faster, and that was thrown by Velasquez, the pitcher given up for Giles.

Last year alone, Giles threw 37 such pitches.

And now, the bullpen appears complete. With Giles closing, Gregerson becomes the right-handed set-up man. Their left-handed relief ace, Tony Sipp, was re-signed by the team this winter, re-joining veterans Will Harris and free agent signee from last offseason Pat Neshek.

Giles solidifies a bullpen that was great early but leaked oil down the stretch in 2015, adding velocity they haven't seen since the glory days of Nolan Ryan.