When Lucas Sims was the best reliever in baseball

This time last year, Lucas Sims was already suffering debilitating back spasms. The twinges then turned into sustained nerve pain and his eventual loss of motor skills to numbness. Sims began the 2022 season on the Injured List. In late April, with the Reds in the midst of their 3-22 tailspin, he attempted a return. Still hobbled, Sims was nowhere near the same pitcher.

He lasted a couple weeks. On May 12, the Reds put Lucas Sims back on the IL where he would remain for the rest of the season. The reliever underwent surgery last July to repair a bulging disc.

In case you hadn’t heard, Lucas Sims is pitching again this spring. It’s with a healthy lower back.

But this post has nothing to do with his back or the 2023 season. Instead, it’s a celebration of the two remarkable months when Lucas Sims was the best reliever in baseball.

Origin Story The Reds didn’t draft Lucas Sims. At the 2018 summer deadline, they traded outfielder Adam Duvall to Atlanta for three players. Reds president of baseball operations Dick Williams said at the time he viewed Lucas Sims as the centerpiece of the deal. Over the next twelve months, the 24-year-old Sims shuttled between Triple-A Louisville and the Reds. His call-up in July 2019 would be for good. The Georgia native appeared in 24 Reds games in 2019, including four starts, and 20 more in the COVID-abbreviated 2020 season. From May 2019 through June 2021, Lucas Sims pitched in 72 games for the Reds. In those 97 innings, his strikeout rate was 33.3% while the league average was 24%. Sims’ walk-rate over that time was 11%, a bit higher than the 10% average by major league relievers.

On June 24, 2021, Sims went on the Injured List for a sprained right elbow.

What Happened Next Sims returned to the Reds roster six weeks later. The Reds’ record was 61-51 and David Bell’s team was headed for a second consecutive trip to the postseason, that is until the Cardinals somehow won 17 games in a row. Lucas Sims made 19 appearances from August 9 through the end of the 2021 season. A total of 339 Major League relievers threw at least 100 pitches in that span.

Lucas Sims was better than all the others.

Dominance Sims faced 69 batters over those 18+ innings. He struck out 32. That’s a rate of 46.4%. League average for relievers was half that. The second-highest strikeout rate (45.1%) belonged on the Brewers’ Josh Hader. Only three other pitchers were above 40%. Sims induced a swinging strike rate of 15.5% while league relievers averaged 11.7%. The contact rate Sims allowed (65%) was ten points lower than the rest of the league.

Command Free passes had been a minor issue for Sims. But of those 69 batters, Sims walked only three. That’s a walk-rate of 4.3%. Over that same time, Josh Hader walked 14.1%. To further emphasize Sims’ immaculate control those eight weeks, he didn’t hit a batter or throw a wild pitch.

K%-BB% A straightforward way to measure a pitcher’s effectiveness — one that uses back-of-the-baseball-card stats — is to subtract his walk-rate from his strikeout rate (K%-BB%). If you doubt this metric’s power to identify the best pitchers, consider the names at the top of the K%-BB% list from 2022: Ohtani, Cole, Rodon, Nola, Gausman, Burnes, Verlander, Darvish and Bieber.

From August 9 to October 1, 2021 Lucas Sims posted a K%-BB% of 42.0%, again the best in baseball. Second was White Sox closer Liam Hendrix (40.9%). Only one other pitcher was above 33%.

Composite Measures Sims also led in metrics that include batted ball data. His 1.38 SIERA was best. Hendrix was second at 1.44. If you include batted ball quality, only the Mariners’ Casey Sadler edged out Sims. Sadler posted an xwOBA of .182 while Sims clocked in with .185. League average was .309. Only 11 of the 69 batters managed hits off Sims. Here is the breakdown of Sims’ pitch outcomes during his eight weeks at the top.

Portfolio Lucas Sims throws three pitches. He uses a four-seam fastball (95.4 mph) and slider (85.7 mph) about 40% of the time each. The remaining 20% of his pitches are curveballs (82.4 mph). This chart shows the exact breakdown from the fall of 2021.

Fastball Lucas Sims has one of the highest fastball spin rates in the majors. At times, it’s been in the 100th percentile. The elevated spin rate — backspin — keeps the pitch from falling due to gravity as much as it otherwise would. In 2021, Sims’ fastball had a 3.1 inch vertical “rise” compared to the major league average. The average fastball drops 15 inches on the way to the plate. Sims’ heater drops 12 inches. Causing a batter to swing three inches below where the habits of a lifetime tell him to expect it may not seem like much until you realize the diameter of a baseball is 2.9 inches.

Sims built his fastball spin rate from 2300 rpm in 2017 to 2600 rpm in 2021. These heat maps compare the location of Sims’ fastballs in 2021 (left) compared to 2017. Notice how much tighter and higher up in the zone Sims’ pitch was in 2021.


During Lucas Sims’ dominant streak, batters had an expected batting average of .136 on his fastball. League average was .261. Here Sims fires a 96-mph heater up in the zone to Cleveland’s Franmil Reyes.

When fastballs stay up in the zone more than batters expect they also hit underneath it and pop the ball up. The average popup rate for relievers in 2021 was 10.%. During Sims’ strong run, his popup rate was a whopping 27.8%. Here, Sims induces a popup from Pirates (and current Red) infielder Kevin Newman. Follow the path of the pitch as it seems to defy gravity at the end.

Slider Some pitchers have sliders with more vertical (up-down) break than average. Others have more horizontal (to the side) movement. Sims is a rare pitcher whose slider does both. Again, much of this can be attributed to his talent at putting spin on the ball. The league average for sliders in 2021 was 2414 rpm. Sims’ slider that year averaged 2987 rpm, third highest. His whiff rate on the slider in 2021 was an amazing 42%. In 2021, 95% of Sims’ sliders were thrown to right-handed batters.

Here, Sims retires the Brewers’ Lorenzo Cain on a sharp-breaking slider down and away. You might wonder why Cain swung at a pitch so far outside. Watch just after the pitch leaves Sims’ hand how it’s in the strike zone, maybe even on the inside half. That’s why.

Curveball Sims throws what’s known as a “12-to-6” curve, referring to numbers on a clock. That means the pitch breaks straight down. In 2021, compared to league average, his curve averaged more than 4 inches more vertical drop than the the league norm, while at the same time it broke 2.5 fewer inches to the side. Again with the spin, which sharpens the break. In 2021, league average spin on curves was 2462 rpm while Sims was at 3027 rpm. Sims used his curve as an out pitch mainly against lefties. 85% of his curves went to left-handed batters.

Here, the bottom falls out of this Sims curveball that whiffs the Cardinals’ Tommy Edman.

Spin Rate Skepticism You may be wondering about sticky stuff and Lucas Sims. MLB cracked down on pitchers using foreign substances in May and June of 2021. Several notable pitchers, including the Reds Tyler Mahle, saw their pitch spin rates decline across the board after the league toughened its policy. Draw your own conclusions. In Sims’ case, the data was mixed and confounded by him dealing with an elbow issue during the time of increased enforcement. Some of his spin rates went down from 2020 to the end of 2021 but others went up.

The broader point is this. The two months that are the subject of this post occurred well after MLB had tightened control over sticky stuff. So whether or not Sims, or anyone else, used it earlier, umps were checking every night when Lucas Sims was the best reliever in baseball.

Lucas Sims in 2023 Lucas Sims has appeared in three games this spring, pitching a full inning in each. Over three IP he’s struck out five and walked one. Sims says he feels great. Last week, Mo Egger interviewed Dr. Ben Valley, a local spine surgeon. Valley said the risk of recurrence is “not zero, but also not crazy high.”

A healthy spine is terrific news for Lucas Sims. An able-bodied Lucas Sims is likewise an outstanding turn of events for the Reds. Sims is under team control through the 2024 season. He gives David Bell and Derek Johnson an experienced arm to cover high-leverage late-inning situations. Sure, it’s unreasonable to expect Sims to pitch the way he did those two glorious months at the end of 2021. But it’s fun to relive them and know that on any given night, or stretch of nights, Lucas Sims can be the best there is.

Steve Mancuso

Steve Mancuso is a lifelong Reds fan who grew up during the Big Red Machine era. He’s been writing about the Reds for more than ten years. Steve’s fondest memories about the Reds include attending a couple 1975 World Series games, being at Homer Bailey’s second no-hitter and going nuts for Jay Bruce at Clinchmas. Steve was also at all three games of the 2012 NLDS, but it’s too soon to talk about that.

4 Responses

  1. Larry D. Camic says:

    Great content. Sims can be an awesome presence along with Diaz in the Reds bullpen this year. Think they need a couple more lefthanders for the bullpen imo.

    • Steve Mancuso says:

      Thanks. I’ve seen it said the bullpen may be a strength for the Reds this year. If that means relative to the offense, defense and starting pitching, then maybe. If it means relative to other teams, I doubt it. After Diaz and Sims, who’s third, right or left? Buck Farmer? If Cessa is in the bullpen, then he’d be another one. The rest of them — Gibaut, Kuhnel, Cruz — all hit-and-miss. And that’s the RHP. As you say, they are skimpier on the left side. I *guess* you can call Sanmartin proven, but hardly. And then where?

  2. Thomas Green says:

    I love this kind of article.
    As for the bullpen this year, it feels far ahead of last year if health can hold. Two solid pieces for the high leverage innings (but good bullpens have at least this many), but the next (middle) level is missing. The depth is better – as in they won’t have to run out guys who can’t even cut it in AAA (again, pending health).

  3. kmartin says:

    Great writing as always. Well, I can’t resist. In 2014, for his entire season (54 innings), Aroldis Chapman struck out 52.5% of the batters he faced. The second highest was Andrew Miller with 42.6% so Aroldis topped the second best guy by 10 percentage points for his entire season. However his K%-BB% for the season for the season was a “mediocre” 40%. A small sample, but batters swung at his changeup 19 times and hit one fair. Of the 202 batters he faced he gave up 21 hits.