Keys to the game: What each Ray needs to do to succeed in 2018, Part III The Bullpen

So far we’ve given you a some good stats to watch for the Rays lineup and rotation in 2018. Now we’ll finish off with the most volatile part of any team (and thus the hardest to measure statistically): the bullpen.

Jose Alvarado: Average fastball velocity

Alvarado is one of the hardest throwers in baseball. His 98.3 average fastball velocity, per FanGraphs, ranked eighth in baseball last season. If you prefer Statcast, his 95.3 overall pitch velocity ranked sixth in baseball, and if you like taking things one level further, his perceived velocity was topped by only Aroldis Chapman among pitches with at least 100 pitches in 2017.

Once Alvarado learns to harness this fire (and his 11.1 scoreless innings after the All-Star break are certainly a sign — albeit a SSS sign — of that progress) he’s going to be hell on MLB batters. It’s not hard to imagine Alvarado as the Rays closer of the future. (A dream I know I am not alone in having among Rays fans.)

Alex Colome: HR/FB

Colome has done a rather impressive job of limiting the long balls since taking over as the Rays closer, especially last season, when most other pitchers saw their rates spike. Of pitchers with at least 50 innings pitched, Colome ranked 22nd out of 355 in terms of HR/9, trailing only four other closers (Roberto Osuna, Felipe Rivero, Fernando Rodney, and Aroldis Chapman.

Over the past three seasons combined, of the 204 pitchers to throw at least 200 innings, Colome ranks an impressive ninth in fewest home runs allowed per nine innings, fourth among relievers.

The Rays should be thankful that Colome did such a good job keeping the ball in the yard last season, because if he had even been average in terms of long ball prevention, they would have been in trouble. Among the 150 relievers to throw at least 50 innings last season, Colome ranked a far more pedestrian 72nd in WHIP.

Colome’s 4.32 xFIP paints the picture of a pitcher who, if he sees a bit of a regression to the mean in home run rate, may no longer be a viable closing candidate (Colome ranked in the 30th percentile among relievers in terms of xFIP in 2017).

It’s not as if Colome has an extraordinary ground ball rate. It’s solid, with a nice ranking in the 69th percentile, but of the aforementioned group of home run suppressors over the past three seasons, Colome has the second-lowest HR/FB rate, a suggestion that he may be getting a bit lucky.

Piggy-backing on that is the idea that his hard hit ball rate is far from outstanding (23rd percentile), and even the past three seasons of 223.0 IP is still a small enough sample size that his running success in terms of limiting the long ball could still be a bit noisy instead of a real skill.

It would be glorious if Colome were to prove the past few paragraphs idiotic in 2018 with another season of strong home run suppression, it’s just something to make sure to look for.

Sergio Romo: xwOBA-wOBA

The trendiest metric on the market these days (with pitch tunneling ready to take the crown once we get some more data on that front), it’s mostly a good news scenario here for Romo. The 35-year-old California native ingratiated himself with the Rays faithful thanks to a strong final ten weeks of the season last year, and he’ll be back in 2018 to prove that was no fluke.

Romo posted a 1.47 ERA in his 30.2 innings with Tampa Bay, a figure that ranked sixth among all 250 pitchers with at least 30 post-All-Star break innings last year.

As noted, with Romo, it’s a good news/slightly-cold-shower news situation in regards to Statcast’s shiny xwOBA metric. As MLB.com defines xwOBA:

“Expected weighted on-base average (xwOBA) is formulated using exit velocity and launch angle, two metrics measured by Statcast.”

Basically, the stat is attempting to drill even further in terms of the contact a pitcher allows. It is likely unsurprising that by xwOBA-wOBA, Romo got a bit lucky in 2017. Only two Rays (Chih-Wei Hu in 10.0 innings and Chase Whitley) saw a bigger difference in the wOBA they allowed and the wOBA they “deserved to allow” based on the launch angle and exit velocity of their contact allowed.

That’s the slightly-cold-shower news.

But fans aren’t expecting Romo to come out and twirl a 1.47 ERA again in 2018 (at least they shouldn’t be). That’s where the good news comes in. Romo still had an excellent xwOBA overall (.254). That figure ranked second to Tommy Hunter on the team last year (minimum 100 balls in play), and would have ranked in the top 50 among all pitchers in baseball last season. There’s a lot to like with the Romo re-signing.

Daniel Hudson: Slider usage

Between Carl and JT, we’ve covered the Rays most recent bullpen addition pretty well this spring.

Chaz Roe: Spin rate

And while we’re giving out links to strong writing, here’s Jeff Sullivan on Chaz Roe and his crazy slider.

I’ll just add that the spin rate hasn’t going anywhere since that article, as Roe ranked eighth in baseball by average spin rate last season. Last year was also the third straight season in which his slider usage went up, proving that there is indeed no such thing as too much of a good slider.

Ryne Stanek: Hard hit ball rate

Stanek will provide the flames from the right side of the mound, to match Alvarado’s heat from the left. Stanek’s average pitch velocity, per Statcast, was a tenth of a mile per hour lower than Alvarado, while FanGraphs pegged Stanek’s fastball as two-tenths of a mile per hour “slower” than Alvarado’s.

In Stanek’s case, however, it was the age-old “the faster it comes in, the faster it goes out” axiom brought to life. In his admittedly tiny 20.0 MLB innings, Stanek allowed an absurd 44.4 percent hard hit ball rate and 3.7 percent soft hit ball rate. Now, we’re dealing with fewer than 100 batters faced, but both of those figures would have been (easily) the worst among all qualified pitchers in 2017. Now the likelihood that Stanek ends a full season with those figures is highly unlikely (the biggest negative gap between hard hit and soft hit ball rates, even among relievers, over the past decade was 28.5% by Shane Greene last season), but in order to be an actually successful bullpen arm, Stanek will have to go beyond just “not worst of the past ten years.” He’ll need to do a better job commanding his fastball and picking his spots in terms of when to attack and when to waste a pitch, thus limiting some of that crazy-hard contact he allowed in 2017.

Dan Jennings: Average launch angle

Jennings was another reliever who came to the Rays midway through 2017 and will (presumably) be a full-season contributor in 2018. Jennings had a solid 3.44 ERA with the club, with only one real blow-up (four earned in one inning against Boston) and lots of solid performances.

One way that Jennings thrived was by keeping the ball on the ground. With a ground ball rate of 59.8 percent, Jennings improved on what was already a strength for the 6’ 3” lefty (55.2 percent career ground ball rate).

Another way of looking at the type of contact Jennings allowed is to use Statcast to look at the average launch angle that Jennings induced in his 2017 Rays batters faced. With an average launch angle of 1.4 degrees, Jennings had the lowest launch angle allowed of any Rays pitcher with at least 50 balls put into play. There’s plenty of good to be found at the other end of the spectrum, if pitchers are able to induce pop ups or lazy fly balls, but getting batters to pound the ball into the ground is always a good sign for a pitcher without overwhelming stuff, and it will be key once again in 2018 for Jennings.