Waiting out the free agent market did not work into the favor of Trevor Rosenthal but he's going to replace Liam Hendriks in Oakland on a one-year contract. After struggling with his command returning from Tommy John surgery in 2019, Rosenthal bounced back with former Cardinals manager Mike Matheny in Kansas City. Rosenthal notched seven saves over 14 appearances with the Royals prior to his trade to San Diego. All told, Rosenthal finished 2020 with a win, 11 saves, a 38:8 K:BB, 1.90 ERA, 2.31 SIERA and 0.85 WHIP over 23.2 innings of work.

Albeit in a shortened season, Rosenthal set career bests in both of his ratio statistics along with swinging strike percentage, contact rate, Z-Contact (in the strike zone) percent allowed and O-Swing (outside the strike zone) percent. He almost came full circle to his strong 2017 prior to his surgery in most categories so it's not like Rosenthal displayed skills out of nowhere:

Year

G

IP

Saves

ERA

WHIP

K

BB

SwStr%

Contact%

SIERA

2017

50

47.2

11

3.40

1.20

76

20

15.9

67.9

2.60

2020

23

23.2

11

1.90

0.85

38

8

16.5

64

2.31

Using this as a baseline for 2021, exploring his data on Statcast unfolds more information on Rosenthal. According to Statcast, Rosenthal allowed 44 batted ball events including three barrels (6.8 percent), an 90.5 MPH average exit velocity and a 40.9 hard hit percentage. Beneath his surface numbers, Rosenthal's expected numbers also shined last year with a 2.00 expected earned run average (xERA), .132 expected batting average (xBA) and minuscule .210 expected weighted on-base average (xwOBA). Depressing runners on base remains a key to success in high leverage.

With improved command in 2020 further from his surgery rehab, Rosenthal returned to past levels with his arsenal. First, here's a visual displaying all of his swinging strikes from last year:

Unpacking his pitches to sort out how effective each one proved to be, here's his pitches by type with some eye popping numbers:

- Rosenthal Four-Seam: 67.5 percent usage, .197 xwOBA, 35 whiff percentage, 41.7 K%, 37.3 put away percent

- Rosenthal Slider: 20.5 percent usage, .227 xwOBA, 36.1 whiff percentage, 30 K%, 19.4 put away percent

- Rosenthal Change-up: 8.4 percent usage, .000 xwOBA, 80 whiff percentage, 100 K%, 46.2 put away percent

In comparison to 2017, Rosenthal increased his whiff percentage to 37.7-percent last year from 34.9-percent despite generating a lower swing rate. He produced a 40.9 ground ball percentage while giving up fly balls in 34.1-percent of his batted ball data and only a 20.5 line drive rate. Going to Oakland could insulate too much regression in terms of home runs, especially since Rosenthal induced 50-percent of his batted balls to the center of the field.

Noting it's a small sample size, Rosenthal ranks as follows against his peers last season:

- 99th percentile in xwOBA, xBA, K%, xERA and Fastball Velocity (98 MPH on average)

- 98th percentile in expected slugging percentage

- 95th percentile in whiff rate

When viewing how effective Rosenthal's four-seam fastball ranked in 2020, here's the top-10 including the pitcher he projects to replace in Oakland's bullpen:

Before exploring his projections, Rosenthal's pitches on Brooks Baseball yielded swinging strike percentages and ground ball rates as follows:

- Rosenthal Four-Seam: 14.8 SwStr%, 39.5 GB%

- Rosenthal Slider: 17.7 SwStr%, 41.2 GB%

- Rosenthal Change-up: 18.6 SwStr%, no batted ball data for GB%

In 2017, Rosenthal's change-up generated a 26.4 swinging strike percentage so if he throws this pitch more often in Oakland it could unlock even more strikeouts for a pitcher who recorded a 41.8 strikeout percentage in 2020. Not too shabby.

Due to a lack of data along with a horrific 2019 campaign, Rosenthal's projection sets provide a low baseline:

It's easy to forget but Rosenthal's numbers with St. Louis needs to be accounted for before letting him drift in drafts, which will be unlikely with the news of him landing in Oakland to close. Still, here's his career numbers with St. Louis:

- Trevor Rosenthal as a Cardinal: 11-24, 121 Saves, 328 games, 325 IP, 435:143 K:BB, 2.99 ERA, 2.60 FIP, 1.31 WHIP, 31.2 K%, 10.3 BB%

Plan on some migration to the mean in regards to Rosenthal's ERA and WHIP in 2021 but if he continues to rack up strikeouts, he could notch 25-to-30 saves with an ERA in the low three's and a WHIP between 1.18-to-1.22. Best of all, he should receive a majority of save chances in an ever changing saves landscape. So ignore the projections and trust his stuff, especially the high octane four-seam fastball. Saddle up.

Statistical Credits:

Fangraphs.com

BaseballSavant.com

BrooksBaseball.net

THE BAT courtesy of Derek Carty

ATC courtesy of Ariel Cohen

Steamerprojections.com

ZiPS courtesy of Dan Szymborski

Baseball-Reference.com