Most baseball fans are unfamiliar with the relief pitchers who break onto the MLB scene each season. Increasingly, these bullpen arms come equipped with high-90s fastballs and knee-buckling breaking pitches, but their status as low-end prospects often shields them from the scrutiny of their more prominent rookie counterparts.
Last year, breakthrough relief pitchers included Lou Trivino (A’s), Seranthony Dominguez (Phillies) and Richard Rodriguez (Pirates), each of whom brought little to no fanfare to the league but quickly became essential members of their respective teams. This year, they’re entrenched in late-inning roles.
The 2019 wave of relievers figures to be similarly potent, and already several have distinguished themselves. The group includes Marlins right-hander Nick Anderson, Padres right-hander Trey Wingenter and Mariners right-hander Ryan Sadzeck.
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Here’s a list of the top fastball velocities, via Statcast, of rookie relief pitchers. Their 2019 ERA and FIP marks are also included, though early season small sample noise makes those statistics somewhat fluky.
| Rookie relief pitcher | Average fastball velocity | ERA | FIP |
| Trey Wingenter (Padres) | 96.6 mph | 3.27 | 4.12 |
| Josh James (Astros) | 96.5 mph | 7.11 | 5.64 |
| Connor Sadzeck (Mariners) | 96.4 mph | 1.13 | 1.99 |
| Ty Buttrey (Angels) | 96 mph | 0.75 | 1.20 |
| Yoan López (Diamondbacks) | 95.9 mph | 0.96 | 4.08 |
| Nick Anderson (Marlins) | 95.5 mph | 2.45 | 2.30 |
Of course, fastball velocity does not mean everything. Plenty of MLB pitchers without proper control have wasted their heat and not established a lasting big-league career. Others with relatively low velocity but enough other positive qualities have still become elite. In general, though, hard fastballs portend better pitching results and elevated strikeout rates.
At least one or two of the above relief pitchers should solidify into dependable late-game options.
Anderson in particular stands out, not just because his raw stuff is complemented by on-field results, but also because his strong heater is paired with a devastating slider. Through 11 appearances this year, Anderson has struck out 18 batters per nine innings.
Though he's started the season in low-leverage roles (as many rookie relief pitchers do), he’s pushing for greater responsibilities. It’s possible he becomes Miami’s setup man or closer in a short time. After all, right-hander Sergio Romo has a 6.75 ERA at the back of the the Marlins' bullpen, and he might not be trusted in save situations much longer. Tayron Guerrero is seemingly another option, but he struggled with control as a rookie in 2018.
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Elsewhere, Wingenter appears a potential stud behind Kirby Yates and Craig Stammen. He posted absurd strikeout rates throughout his minor league career, and he has carried that trait to MLB, striking out 12.1 per nine innings in 33 career appearances.
Like Anderson, Wingenter is purely a fastball-slider guy at this point, but that combination has proved effective. Opponents are whiffing on the slider 61 percent of the time in the early going this year.
Sadzeck, meanwhile, offers a curveball and sinker in addition to the fastball-slider combo, though he's cut back on those secondary pitches in recent weeks. He's struck out 10.13 batters per nine innings this year and delivered the best ERA and FIP of the group.
All six hard-throwing rookie relief pitchers are worth watching as the campaign progresses. They're bound to provide fans a jolt — either from lockdown performances or because they can't find the strikezone.
In any case, the newest crop of bullpen weapons figures to be just as potential-filled as the last.