Moving Forward: Should Roberto Osuna or Hector Rondon Close Out Games for the Astros?

There are certainly valid reasons Houston Astros fans never want to see Roberto Osuna closing games for their favorite team (or any team, really). For a moment, however, let’s briefly put aside Osuna’s current legal situation to entertain a baseball-related question about the backend of the Astros bullpen: Who should be the closer?

Prior to the Osuna trade, the Astros already had a guy who established himself as a bonafide stopper, both this year and in previous seasons. Hector Rondon has 90 saves in his Major-League career and he has converted 13 opportunities for the Astros this season.

According to FanGraphs, Rondon is tied with Collin McHugh for the highest WAR amongst Astros’ relievers and in line with other elite closers, like Boston’s Craig Kimbrel, Cleveland’s Brad Hand, and the Los Angeles Dodgers’ Kenley Jansen. Good company, and those aren’t the only numbers indicating the divide between Rondon and Osuna isn’t the gaping chasm you might imagine.

Rondon has 11.13 K/9 this season, a full strikeout higher than Osuna’s career average of 10.11 K/9. In fact, Rondon has pretty much increased his K/9 rate every season in the Majors and his strikeout-percentage (30.7%) is as high as it’s ever been (Osuna’s is lower than ever at 19.2%). Rondon was a pretty good closer for the Cubs before he started allowing homers at a much higher rate in 2016 and 2017 than he had previously.

Rondon has improved in that regard this year as well; his HR/9 rate in 2018 (0.62) is a huge reduction from last year, when he surrendered 1.57 HR/9, and slightly less than Osuna’s career average (0.75). Rondon has also given up hard contact at a far lower rate than Osuna, both this season and overall (30.9% vs 38.3% in 2018; 27.4% vs. 31.3% career).

The question mark with Rondon has typically been his ability to command the strike zone. Rondon’s K/BB ratio sits at 4.50 this season and is below four over the course of his career (for reference, Rondon’s K/BB rate was similar to Ken Giles coming into the season). Osuna has a K/BB rate over six for his career and he’s only walked one batter in his 19.1 combined innings of work for Toronto and Houston in 2018.

For those who prefer K%-BB% (it tends to be less skewed than K/BB rate), Osuna has Rondon beat there over the course of their careers, too. Osuna’s K%-BB% (24.3%) is about six percentage-points better than Rondon’s (18.8%), although that trend has reversed this season (18.0% and 23.9%, respectively).

Osuna’s return to the Majors—albeit a small sample—had been clean on-the-field until Sunday afternoon, when he was saddled with the loss after allowing a Mitch Hanger RBI-double in the top of the tenth inning. (An inning earlier, Rondon failed to convert the save opportunity when Ryon Healy lofted a game-tying, solo homerun to the Crawford Boxes. Thanks for putting a dent in my argument, Healy.)

Osuna has tossed four innings since joining the Astros and issued zero walks, but he has only struck out two of 15 batters faced. It’s reasonable to expect Osuna will need some time to return to peak form, but it’s vitally important for relievers—especially in the postseason—to keep opposing hitters from putting the ball in play (See: 8th inning of Royals- Astros 2015 ALDS, Game 4).

In 2015 and 2016, nearly half of the batted balls put in play against Osuna were of the flyball variety. He has changed that trend over the last two years and brought his flyball-percentage down to a career-low 30.5% this season (again, small sample). Even so, Rondon has traditionally been much more of a groundball pitcher than Osuna. For his career, Rondon has averaged 1.52 groundballs per flyball compared to 0.91 for Osuna, although, again, the latter has improved substantially the last two years in that regard.

Personally, I find a lot of value in relievers who can overpower hitters or are one pitch away from getting out of a jam at any moment (e.g., GIDP)—particularly when being asked to get multi-inning saves, as is common in the playoffs. Somewhat surprisingly, Rondon has better strikeout numbers in his career than Osuna and is punching out guys more often than he ever has. Rondon has also shown a greater proclivity to induce groundballs than Osuna.

Although it seems crazy for the Astros to expose the club to the backlash of acquiring Osuna merely to use him as a set-up guy, the numbers don’t clearly indicate he’s a significantly better option as a closer than Rondon. In fact, Rondon appears to have the edge over Osuna in a few categories. I’m not arguing for Rondon to be the closer permanently; I believe Osuna should be integrated into that role next Spring (assuming his legal issues are resolved) and be expected to operate as a shutdown closer for the remainder of his Astros tenure.

For the rest of this season, I do believe there is a case for Rondon to retain his role as the incumbent closer. Given the issues the Astros have had closing games since last postseason, having two excellent options to preserve late leads is likely a welcome problem and probably a big part of the reason they made the trade for Osuna.

Note: All statistics were calculated after games played on 8/12/18