KC Royals: What to expect from Trevor Rosenthal signing

The KC Royals signed Trevor Rosenthal to a minor league contract laden with performance incentives and an invite to Spring Training. What can we expect from the once dominant reliever out of the Royals bullpen in 2020?

The Kansas City Royals are attempting to sign low cost/high reward bullpen arms this offseason to stockpile a battered and beleaguered 2019 bullpen. On Saturday, the Royals signed Trevor Rosenthal to a $2 million-dollar minor league contract with an added $2.25 million in performance incentives.

The 29-year-old (30 in May) Rosenthal is a seven-year MLB veteran, who was one of the more dominant relievers during his time with the St Louis Cardinals between 2012 – 2015.

Rosenthal began to struggle with the Cardinals during the 2016 and 2017 seasons, losing his closer role in the process. Rosenthal has a career stat line in the MLB of 340.1 innings of 3.46 ERA, 2.79 FIP, 1.355 WHIP, 452 Ks, and 121 saves with an All-Star team selection in 2015.

In August of 2017, Rosenthal injured his UCL in his right elbow requiring Tommy John surgery. Rosenthal didn’t pitch at all in 2018, as he rehabbed back from the injury.

Rosenthal returned back to action in 2019 with the Detroit Tigers and Washington Nationals and had an ugly 2019, pitching 15.1 innings of 13.50 ERA, with 17 strikeouts and 26 walks. Rosenthal also pitched 15.0 innings split between AA and AAA in the Tigers organization and Yankees organization. Those 15.0 minor league innings saw Rosenthal pitch to a 9.60 ERA with 20 strikeouts and 16 walks.

The last thing that tends to come back for pitchers recovering from Tommy John surgery is command and Rosenthal’s 2019 highlighted his struggle to find his feel and command. In 30.1 innings between the MLB/AAA/AA levels, Rosenthal walked 42 batters and hit nine batters.

Rosenthal was able to regain his velocity in 2019 coming back from rehabilitation. Prior to Rosenthal’s UCL injury in 2017 he was reaching the following average velocities: fastball – 98.4 mph, cutter – 86.5 mph, and change-up – 87.6 mph. His return in 2019 saw his average velocities return to: fastball – 98.0 mph, cutter – 88.1 mph, and change-up – 87.8 mph.

It was apparent in his pitch selections in 2019 that Rosenthal didn’t have his feel back, as he only threw his change-up 3.2% of the time in his outings compared to his 12.5% in 2017. Throwing an effective change-up is heavily dependent on feel and confidence in the pitcher. Rosenthal’s change-up was pitch valued at -0.2 while for his career his change-up pitch value averaged 3.23.


Trevor Rosenthal still possesses closer type stuff out of the bullpen. If he can rediscover his feel and command, he has a chance to become an outstanding low cost/high reward free agent signing for the KC Royals bullpen in 2020. A reasonable expectation for Rosenthal in 2020 would be an ERA in the 3.50 – 4.00 range with 10.0 K/9, and a 1.30 WHIP.

Rosenthal has a chance to far exceed this expectation if he finds his command, as his stuff is still that good. His hard-late breaking cutter couples well with his elite velocity fastball. His change-up is effective when he has the feel for it to disrupt the timing of hitters sitting on his fastball.

If Trevor Rosenthal can find his form, there’s a possibility he could return to his 2015 All-Star numbers when he had 68.2 innings of 2.10 ERA, 1.267 WHIP, 83 Ks, and 48 saves in 51 chances.

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