Mike Shildt, Andrew Miller and the Winter Meetings

Andrew Miller signed with the St. Louis Cardinals for two years, $22 million with a third year vesting option on Dec. 21, 2018. The deal came days after the Winter Meetings ended in Las Vegas.

“It would be great to add some help,” Shildt said at the Winter Meetings on Dec. 14. “Especially with the lefties in our division, because every club has got some real thump and guys you have to plan for on the left side.”

Mike Girsch and John Mozeliak listened. Or, Shildt had an idea of the Cardinals recent contacts and didn’t want to spoil the surprise. The latter is likely correct, but the former makes for a much better opening. Manager press conferences at the Winter Meeting are often mundane half-hours of regurgitated babble. But sometimes they provide subtle, valid information about a team’s offseason targets.

Analysts--most notably Craig Edwards--believe the Miller signing leaves little room for surplus value. The Cardinals invested in a 33-year-old arm with declining velocity who they hope can return value equal to his contract and if they’re lucky, a bit more. The downside is a repeat of 2018, where Miller is worth about .5 WAR. In that case, he stands little chance of recouping the full value of his contract come 2020. We can criticize the signing as paying for ceiling, but examining the downturn in Miller’s career and the uncharted territory he is entering creates some hope that Miller is a worthy gamble.

After two seasons of dominance, Miller experienced a sharp drop in production in 2018. John LaRue detailed this well for Viva El Birdos in December, pointing out Miller’s falling strikeout rate, rising walk rate, and inability to generate swinging strikes at an elite level. Miller lost just under one mph on both his fastball and slider from 2017 to 2018. The shape of each pitch changed slightly as well.

Baseball Savant

Miller’s slider added more vertical movement, evidenced by the yellow dot moving south in the GIF above. The pitch, however, lost some of its swing-and-miss ability with its whiff rate falling 9 percent according to Baseball Prospectus. His fastball lost some of its patented glove-side movement too, evidenced by the red dot moving slightly towards the center line in the GIF above.

A fundamental change in pitch shape is a good explanation for a variation in effectiveness of a pitch. If Miller was used to throwing sliders with a certain amount of break and that break changes, if all else remains the same, the pitch is ending up in a different spot in the zone. There is a chance this happened with his slider, particularly against left-handed hitters.

Baseball Savant

While the offering ended up off the plate most of the time, Miller started missing on the location of some sliders to left-handed hitters, leaving them over the plate and slightly up in the zone. As a result, left-handed hitters posted a wOBA 74 points higher against Miller’s slider in 2018 compared to 2017 (.240 to .314). For comparison’s sake, the average wOBA in baseball last season sat at .315, showing Miller’s fall from elite to average.

Miller’s 2018 struggle extended to right-handed hitters as well, the handedness he historically dominated during his 2016 and 2017 seasons. The average exit velocity against his fastball rose from 82.9 mph to 89.8 mph between 2017 and 2018. This cut him from the 94th percentile among pitchers in 2017 to the 55th percentile in 2018 (min. 10 batted ball results). He went from elite to average in a matter of months.

There are two logical causes for Miller’s struggle: aging and injury.

Injuries limited Miller to only 34 total innings in 2018 due to three separate disabled-list stints—two for his knee and one for his shoulder. The appearances comprising his 2018 are separate one-month samples with intermittent injury breaks. His 2018 timeline says it all.

• Apr. 25 - Left game with left hamstring injury
• Apr 26 - Placed on 10-day DL, left hamstring strain
• May 11 - Activated from DL
• May 26 - Place on 10-day DL, right knee strain
• July 20 - Announced he needs more rehab appearances
• Aug. 3 - Activated from DL
• Aug. 29 - 10-day DL, left shoulder impingement, received cortisone shot
• Sept. 10 - Activated from 10-day DL
• Nov. 5 - Mark Rodgers, Miller’s agent, says he’s fully healthy

There’s a real chance the majority of Miller’s results in 2018 are skewed by these various injuries. In contrast, however, when Miller presumably regained health in September for his final stretch of appearances, his fastball or slider velocity didn’t tick up to pre-2018 levels. Miller’s slider usage did jump to 63 percent in when he returned from his shoulder impingement, a 16 percent jump compared to the rest of his season. For comparison, Miller’s highest used sliders at his most frequent rate in 2016, when he touched 60 percent on the season. Below, observe the spike above the reference line starting around game 150.

Fangraphs

Even with these signs of success across a small sample of healthy (hopefully) games, he collapsed in his last outing of the season against the Kansas City Royals, leaving little room for a clear resurgence narrative. We’re left with only Mark Rodgers’ words, the Cardinals due diligence and an increase in slider usage for comfort that Miller is healthy. Otherwise, Miller’s pedigree and pitch mix with the context of his age are uncharted territory for a team to project.

By sorting all relievers who accumulated 100 or more innings between 2012 and 2018, we are presented 278 names (Miller ranks third with a 2.24 FIP). Only six of those relievers threw sliders more than 50 percent of the time. Two of those six had fastball and slider velocities in the realm of Miller: Al Alburquerque and Carlos Marmol. The issue is neither of that duo had extended success and both last appeared in a major league game before they turned 32. Miller is already 33.

If we adjust this search to only include relievers with 50 or more innings between 2016 and 2018, we see seven relievers with 50 percent or more sliders and velocities similar to Miller’s. Each still, however, doesn’t provide any context for how Miller might age or how he needs to adjust.

Anthony Swarzak, 33, experienced harder regression than Miller between 2017 and 2018. Boone Logan, 34, has actually increased his velocity every season since 2014 but has never posted a season above a single WAR. Chaz Roe, 32, has been a high-strikeout pitcher for three seasons ever since he jumped his slider usage above 50 percent, but his ability to generate swing and miss off his slider has never been on Miller’s level of consistency. Sergio Romo, 35, is the only pitcher with prolonged success using a fastball-slider combination past the age of 33, but each isn’t near Miller’s tier of velocity. The only tip we have from Romo is his decision to increase his changeup usage past 10 percent for the first time in his career during 2018 to salvage a .5-WAR season with the Rays. Adding a new pitch could be an option for Miller, but again, he has historically been better versus right-handed hitters. The need for a left-on-right changeup is not high.

There isn’t much precedent to show what Miller should do to regain his form. He is a pioneer in this high velocity fastball-slider space, especially for his age. He will also become a reference point for how slider-heavy relievers age in the era of increased breaking ball usage. Miller’s 2019 could reveal the blueprint for post-peak relievers maintain effectiveness, even if he generates little surplus value in the process.