Major League Baseball

One month in, who are the surprise relievers lighting up baseball?

Published May. 6, 2021 10:52 a.m. ET

By Jordan Shusterman
FOX Sports MLB Writer

Ah, the bullpen.

No matter how many years go by or how much smarter baseball teams get, building a successful, consistent, reliable bullpen continues to be one of the game’s greatest challenges — an ever-evolving mystery to solve.

This is because relievers by nature operate in small samples and high leverage, making each performance more likely to be scrutinized but also harder to fully analyze and understand. The number of relievers who are actually good (and healthy) for multiple years at a time is very small, which means every year brings us a whole new cast of late-inning arms with which to familiarize ourselves in short order.

This year is no exception. It’s time to get to know some relievers who are off to great starts in 2021, where the heck they came from and how much we should expect to pay attention to them for the remainder of the season.

J.P. Feyereisen

You already know about Brewers starters Corbin Burnes and Brandon Woodruff and the 1-2 punch of Josh Hader and Devin Williams at the back of Craig Counsell’s bullpen. But Feyereisen has been the real breakout so far in 2021, and if you looked at his minor-league numbers, you might wonder why this didn’t happen sooner.

Drafted by Cleveland, the right-hander was sent to the Yankees as part of the Andrew Miller deal in 2016, and over the next three seasons, he posted a 3.12 ERA in 164.2 IP, with 195 strikeouts in Triple-A. That’s italicized because what else did the Yankees want him to do? For two-plus seasons, Feyereisen was proving his ability at the highest level of the minors, but the Yankees never gave him a shot — not a single inning! — before trading him to Milwaukee in September 2019.

Making the Feyereisen story even better is that he is a proud Sconnie through and through, having grown up in River Falls, Wisconsin, and been drafted out of D-III Wisconsin-Stevens Point. Now he’s the reliever with the most appearances without allowing an earned run in 2021, and you can be sure he won’t be heading back to Triple-A anytime soon.

Kendall Graveman

The journey from average starter to dominant reliever is hardly an uncommon one, with countless examples in recent years. But Graveman's transformation from, stylistically and statistically, one of the more generic starting pitchers in baseball to the fire-breathing sinker-baller he is now for the Mariners is downright shocking.

From 2015 to '17, Graveman made 71 starts for Oakland, He averaged about 92 mph on his sinker, relied heavily on a cutter and occasionally mixed in a changeup or slider. He posted a 4.11 ERA in 407 innings, good for a 99 park-adjusted ERA+ (league average is 100).

He was Kendall Graveman, regular ol’ No. 4 starter.

Then, in 2018, Graveman had Tommy John surgery. He signed with Seattle after the 2019 season, with the idea that he could compete for a rotation spot. He made two starts at the beginning of the 2020 season before things took an unexpected and scary turn.

In August, Graveman revealed that had been dealing with pain caused by a benign bone tumor in his cervical spine that he learned about in 2019. He and the team made the mutual decision to have him return strictly as a reliever to ensure a more relatively pain-free pitching schedule.

Graveman re-signed with Seattle this past offseason, citing newfound comfort with the organization and excitement to help lead a young Mariners pitching staff back to the postseason. The stats from his 10 relief appearances in 2020 were hardly anything to write home about, but you could start to see how special his fastball could be in shorter bursts, and now we’re seeing it in full force.

Graveman has been the bonafide star of a shockingly improved Seattle bullpen.

Caleb Thielbar

I know Minnesota has been one of the biggest disappointments in baseball this season, and the bullpen has contributed to some of those frustrating losses, but we have to talk about Thielbar. Twins fans are plenty familiar with the lefty, as he was a solid reliever back in 2013 and '14. Then he ... kinda disappeared?

The Minnesota native bounced around a few organizations, even pitching for the then-independent St. Paul Saints for a couple of seasons before deciding to join the coaching staff of Augustana University, a D-II school in South Dakota, in 2019. Four years removed from his last big-league appearance, Thielbar’s career appeared over.

Then his former team called.

Thielbar signed back with the Twins before the 2020 season and has emerged as one of their go-to relievers as if we’re right back in 2014.

For reference, in the last big-league game Thielbar pitched in before his return to the Twin Cities in 2020, Trevor May started the game, and Torii Hunter was batting second.

The best part of it all: Thielbar still appears on the Augustana website as a coach It’s even in his Twitter bio! I'm not sure how many active big leaguers are out there coaching D-II on the side, but now we know of at least one. Cheers to you, Caleb Thielbar.

César Valdez

Look, we tried to warn you.

We told you that this 36-year-old LIDOM legend and professional baseball journeyman throwing a pitch called "The Dead Fish" would catch your attention at some point this season. But I feel pretty comfortable saying that not even the biggest Valdez fanatics could have foreseen this level of performance from the crafty right-hander.

He now sports a 1.29 ERA in 21 appearances with Baltimore dating to last season, with 10 (!!!) saves despite his having not thrown a pitch harder than 87.4 mph and relying on 80% changeups. With most dominant back-of-the-bullpen arms known for overpowering hitters, those tasked with facing Valdez in the ninth inning are often left stumbling out of the batter’s box dazed and confused, utterly perplexed by their inability to connect with his slow/slower/slowest repertoire.

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It is honestly one of the funnier things to watch in all of baseball today, and as incredible as it sounds when I type it or say it out loud: You should really tune in for the ninth inning of a 2021 Baltimore Orioles game. You won’t be disappointed.

Garrett Whitlock

Another changeup specialist, though this guy can also touch 98 mph, Whitlock has been the other huge Rule 5 success story this season, alongside Tigers outfielder Akil Baddoo. Unlike Baddoo, who had zero success in the upper minors, Whitlock was really solid for 14 starts in Double-A Trenton in 2019 before his season was cut short due to Tommy John surgery.

A former 18th-round pick by the Yankees out of Alabama-Birmingham, Whitlock was hardly a top prospect at the time of his surgery, but his stock was certainly rising. With an already crowded 40-man roster and the fact that he was still rehabbing, the Yankees chose not to add him to their 40-man, leaving him unprotected in the Rule 5.

Boston promptly pounced, selecting Whitlock from its biggest rival with the hope that he could handle the jump to the big leagues fresh off TJ rehab. The Red Sox have sure been rewarded for that gamble.

Another thing separating Whitlock from the rest of this group moving forward is the possibility of him joining the Sox's rotation at some point. He has obviously been nails in relief, so they might not want to mess with it, but he was developed as a starter before Tommy John, and he might be able to return to that role if Boston wants to stretch him out more.

Richard Rodríguez

OK, I realize you might not be watching the 2021 Pirates that closely, but did you know that one of their relievers just threw a perfect game? OK, not a perfect game perfect game, but a hidden perfecto across multiple outings.

On Tuesday, Rodríguez registered his eighth consecutive flawless outing when he closed things out against San Diego, completing a stretch totaling nine innings, 27 batters faced and zero baserunners allowed. Unlike most top-tier relievers, the 31-year-old right-hander gets the job done primarily with the use of a fastball that has a well-above-average amount of horizontal movement, especially for a four-seamer.

You won’t see him on PitchingNinja, but Rodríguez has been a huge reason the Pirates have hung around .500 through the first month.

This isn’t completely out of nowhere from Rodriguez, as he has quietly been one of the more reliable relievers in the National League since his first year in Pittsburgh in 2018. He’s the perfect candidate to be moved to a contender come July.

Jordan Shusterman is half of @CespedesBBQ and a baseball analyst for FOX Sports. He lives in Maryland but is a huge Seattle Mariners fan and loves watching the KBO, which means he doesn't get a lot of sleep. You can follow him on Twitter at @j_shusterman_.