Seven Mariner relievers to watch in 2024

We already know which relievers will cover the final three innings for the Mariners. But who will be their supporting cast?

Feb 12, 2024

Barring unforeseen circumstances, Andrés Muñoz, Matt Brash, Gregory Santos, and Gabe Speier will form the backend of the Mariners’ bullpen. But who will be their supporting cast? Will another unheralded reliever emerge to become the next Brash, Speier, Paul Sewald, Kendall Graveman, or Justin Topa for manager Scott Servais?

Honestly, it’s tough to know. Deserved or not, relief pitchers have a long-standing reputation for being volatile from year-to-year. Having said that, there were statistical signs indicating the breakout relievers mentioned above had a chance to be more than what previous results had suggested.

For example, Sewald had a superb 29.2-percent hard-hit rate and a .301 xwOBA during his largest sample of MLB experience in 2018. Similarly, Speier posted a .304 xwOBA and 32.8% hard-hit rate over four seasons and 40 innings with the Royals. Topa also had a history of an excellent xwOBA, plus he boasted a high ground ball rate. His issue was health.

Expected Weighted On-Base Average (xwOBA) uses quality of contact (exit velocity and launch angle) to determine what should’ve happened to batted balls. A key advantage to xwOBA is defense (good or bad) doesn’t influence it. This gives us a truer sense of how a hitter or pitcher is performing. The MLB league-average xwOBA last year was .320

Armed with the knowledge metrics previously provided clues of untapped potential, I thought it’d be fun to undertake a data-driven search for arms to serve as a bridge between the starter and the backend of Seattle’s bullpen. Perhaps along the way, we’ll happen upon a few breakout candidates.

Let’s begin with several holdovers from last year before discussing the new guys.

Trent Thornton

What went well: Thornton’s 28-percent hard-hit rate was 13th-best among 476 pitchers logging at least 30 innings last year. His 4.3-percent barrel rate ranked 42nd.

The North Carolina alum was stingy with free passes. Within our group of 476, Thornton’s 4.8-percent walk rate tied for 28th-lowest with Mariners legend Anthony DeSclafani and current Seattle teammate Bryce Miller.

What to watch for: Despite demonstrating a knack for preventing hard contact, Thornton was hurt by the long ball. The right-hander allowed five home runs to the 103 hitters he faced as a Mariner. This equates to a 4.9-percent home run rate - the MLB average was 3.2-percent.

The sweeper (34.5-percent) was Thornton’s most relied upon pitch just ahead of his four-seam fastball (33.6-percent). Yet, Houston’s fifth round pick in 2015 didn’t enjoy great sweeper success with opponents producing a .316 wOBA and .500 SLG. Still, I believe we could see a turnaround for Thornton in 2024.

And what’s driving my optimism? Several expected stats suggest Thornton should’ve experienced better results with the sweeper. His xBA, xSLG, and xwOBA were noticeably better than his AVG, SLG, and wOBA last year.

If I’m correct, and that’s a big IF, Thornton sees better sweeper outcomes in 2024.

Tayler Saucedo

What went well: Saucedo’s 31.9-percent hard-hit rate wasn’t as low as Thornton’s, but it was good enough to rank 50th. In fact, Thornton and Sewald were the only Mariners with a better hard-hit rate than the 30-year-old.

Unlike Thornton, the Hawaiian-born Saucedo was stingy with home runs. In 207 plate confrontations, he surrendered just two. That’s a one-percent home run rate, tying him for 18th-lowest with several pitchers including Brash.

The left-handed Saucedo wasn’t platoon-challenged last season. Among 111 southpaws facing at least 50 left-handed hitters, his .258 SLG was 16th-best. Versus right-handed hitters, the Tennessee Wesleyan University alum’s .336 SLG ranked 17 of 125 left-handed pitchers.

Saucedo’s 58.5-percent ground ball rate was 18th-highest, just behind Muñoz (59-percent). Among 398 pitchers allowing 50-plus grounders, his .184 opponent AVG tied for 49th-best. Compared to lefties, he ranked 10th - one spot ahead of Houston’s Framber Valdez (.187).

Generating grounders undoubtedly led to more fly balls. Saucedo’s 14.1-percent fly ball rate tied for eighth-lowest. When opponents did put the ball in the air against the Tahoma High School product, he held them to a .158 AVG and .421 SLG - both were top-25 numbers.

An effective sinker was pivotal to Saucedo’s success. Last year, 93 relievers threw at least 200 sinkers. His version yielded a tenth-best .278 SLG, two spots behind baseball’s premier lefty reliever - Josh Hader (.270).

What to watch for: Saucedo’s 11.1-percent walk rate was highest among Seattle hurlers in 2023. This helps explain how a reliever adept at preventing quality contact could have an average-ish .314 xwOBA.

According to Statcast, 247 relievers faced at least 30 hitters with the go-ahead or tying run on base or at the plate. During these situations Saucedo’s .335 wOBA ranked 147th - not nearly as impressive as his other rankings.

Eduard Bazardo

What went well: One day after trading Sewald to Arizona, the Mariners acquired Bazardo in an under-the-radar deal with Baltimore. The 28-year-old bounced between Class-AAA Tacoma and Seattle over the final two months of the season, but performed well during nine appearances with the big-league club.

As a professional, Bazardo has demonstrated good control with a respectable 6.9-percent walk rate in 465.2 combined innings at the MiLB and MLB levels.

During his brief time as a Mariner, Bazardo’s 25.9-percent strikeout was fifth-best on Seattle’s staff in August-September. Ahead of him were Speier (33.8-percent), Muñoz (30.3-percent), Brash (28.4-percent), and Campbell (27-percent).

Bazardo’s .290 xwOBA during his young career is well under the .308 MLB xwOBA over the last three seasons. It places him in the top 20-percent of 903 pitchers facing 100-plus hitters since 2021 - just behind teammate Bryan Woo (.289).

What to watch for: Bazardo’s 38.9-percent hard-hit rate as a Mariner was average-ish. But the right-hander’s 11.1-percent barrel rate was noticeably higher than league-average. To be fair, we’re talking about a teeny sample of 36 batted balls.

In 2022, Bazardo’s slider was a formidable weapon (.154 AVG and 16.7-percent hard-hit rate). In fact, just eight of 218 relievers throwing at least 100 sliders had a lower hard-hit rate than he did. The same wasn’t true last year.

In limited action with Baltimore and Seattle in 2023, Bazardo’s slider yielded a .321 AVG and 23.8-percent hard-hit rate. Perhaps helping the Venezuelan regain and maintain his 2022 slider excellence is part of the Mariners’ grand scheme.

Mauricio Llovera

What went well: Llovera made nine multi-inning appearances last season, including a three-inning stint. On four other occasions, the right-hander went two frames.

Last year, Llovera’s results were suboptimal (41.1-percent hard-hit rate and .339 xwOBA in 35 innings with the Giants and Red Sox). Maybe Seattle believes it can help him recapture the form he flashed in a limited sample two seasons ago.

During the 2022 campaign, Llovera held opponents to an impressive 20.5-percent hard-hit rate and .260 xwOBA in 16.1 innings. The native of El Tigre, Venezuela also boasted a superb 27.8-percent strikeout rate.

What to watch for: Llovera’s sinker was his most-used offering last season (63.1-percent). In fact, only nine pitchers turned to their sinker more frequently than the 27-year-old did. Despite the massive sinker usage, Llovera didn’t experience as much success on ground balls as you might have expected.

After being traded to the Red Sox in July, opponents produced a suboptimal .320 AVG on grounders off Llovera, which was 10th highest in MLB. Perhaps Boston’s infield ranking last in MLB with -39 outs above average (OAA) last year was a causal factor behind these poor results.

Llovera probably won’t miss Fenway Park either. Statcast Park Factors rates Boston’s home field as the second-most favorable venue for hitters over the last three seasons. The extreme home and away splits of the Venezuelan agree.

It’s worth mentioning Llovera missed the second half of the 2022 campaign with a flexor strain. However, he did pitch a combined 77.2 innings at the MiLB and MLB levels last season.

Llovera is out of minor-league options. Since he was previously outrighted by the Phillies in August 2021, he has the right to reject another outright assignment and opt for free agency instead.

Austin Voth

What went well: Thirteen of Voth’s 25 appearances last year were multi-inning affairs; eight lasted two-plus frames.

Voth’s 5.6-percent barrel rate tied for 77th-best among 448 pitchers allowing at least 100 batted balls in 2023. This tied the former Washington Husky with Sewald among others. The MLB barrel rate was 8.1-percent.

Since becoming an Oriole in 2022, Voth pitched well on the road. Not so much at Camden Yards. Perhaps this nugget factored into the decision-making of the Mariners when the team opted to sign the Kentwood High School product this winter.

What to watch for: Voth missed 71 days due to elbow discomfort last year. His new team undoubtedly did its homework before signing the 31-year-old. But it’s a factor worth mentioning. His only other arm-related issue occurred in 2019 when he missed 43 days with a biceps injury.

During six big-league seasons, the right-hander has better numbers as a starting pitcher than as a relief pitcher.

I’m not suggesting Voth can’t or won’t succeed as a reliever in Seattle. But I thought it was appropriate to note the splits illustrated above.

Carlos Vargas

What went well: Vargas’ average four-seam fastball velocity of 99.4 mph was eighth-highest last year. His 98.8 mph sinker also ranked eighth placing him just behind new teammate Gregory Santos (98.9 mph).

In four minor-league seasons, Vargas surrendered 11 home runs to 841 hitters, which equates to an outstanding 1.5-percent home run rate. Once again, the MLB rate last season was 3.2-percent.

What to watch for: Vargas made just five MLB appearances last year - all in April. It’s worth noting Arizona never recalled him despite its bullpen being a glaring weakness for most of the season.

As with many flame-throwing youngsters, mastering his control has been a challenge for Vargas. In 188.2 MiLB innings, the right-hander has an 11.5-percent walk rate. During his brief time as a Diamondback, he walked four hitters in 4.2 frames.

While in Cleveland’s system, Vargas underwent Tommy John surgery, which cost him the 2021 season. The native of the Dominican Republic returned to the mound the following year logging 34.1 innings at the AA and AAA levels.

This may be a nothing-burger, but Vargas’ 17-percent strikeout rate in 37 appearances with Reno last season was a professional low. Perhaps the D-Backs were emphasizing process over results with the 24-year-old.

Jackson Kowar

What went well: With the Royals last year, the average velocity of Kowar’s four-seam fastball was 96.9-mph. Only 22 of 180 relievers with at least 200 four-seamers threw harder than the 33rd overall draft pick of 2018.

Kowar’s four-seam fastball was relatively effective at depressing power. The former Florida Gator’s .398 SLG against the high-velocity offering was considerably better than the MLB SLG versus four-seamers (.457).

What to watch for: Throughout his professional career, Kowar has annually posted double-digit walk rates. Last year, it was a 14.5-percent rate with Class-AAA Wichita and 14.6-percent with Kansas City.

Finally

Assuming Seattle carries the max of 13 pitchers MLB permits, eight will likely be relievers. Muñoz, Brash, Santos, and Speier are the locks. From my perspective, Voth, Thornton, and Saucedo are also well-positioned to break camp with the Mariners. This leaves one spot for the other four relievers we discussed, plus the plethora of bullpen candidates who will be in camp.

Other bullpen candidates

Ty Adcock
Cody Bolton
Collin Snider
Brett de Geus
Joey Krehbiel
Ty Buttrey
Jhonathan Díaz
Kirby Snead
Tyson Miller
Sean Poppen
Heath Hembree

Source: Roster Resource at FanGraphs

This blogger’s choice for the final bullpen spot is Llovera. I like the potential his sinker presents, plus he should enjoy pitching at T-Mobile Park much more than Fenway. He’s also out of options and can’t be outrighted, which are critical planning factors that must be considered.

Bazardo would be a fine choice, too. But with an option remaining, he could begin the season with Class-AAA Tacoma before an inevitable call-up to the big-league club. Vargas (one option remaining) is interesting, although developing better control to pair with his elite velocity should be a priority. The same applies to Kowar (one option remaining).

My Oh My…