Romo is best used as spot reliever and depth

On Wednesday, March 23rd the Seattle Mariners signed 39 year old veteran reliever Sergio Romo to a one-year $2.5 million contract. The right hander is headed into his 15th season as a major leaguer and has been a fairly steady hand out of the bullpen throughout his career.

Overall, Romo tossed 61.2 innings in 2021 with a pitching line of 4.67/4.24/4.57 (ERA/FIP/xFIP) while striking out 8.76 batters per nine and walking 3.06. None of those numbers are particularly exciting or eye popping and that’s why there’s been some public hesitancy around it. While I’m always a fan of stock piling as many talented arms into the bullpen pile as possible, the reliever does have more value than just being another arm.

Romo has been able to generate strikeouts at a better rate against righties (32.7%) over his career than lefties (17.9%). And that continued last season as well; he struck out 18.6% of left handed batters vs. 25.9% against right handed bats. That difference in strike out rate is also mirrored by walk rate (12.4% vs. 5.6%) and OBP (.330 vs .290).


Now, how has Romo been able to do this? Looking at the heat maps below, it’s pretty clear that he has had better command against right handed bats than he has against left handed.

It wouldn’t surprise me if you consistently see the 39 year old being brought in to get an out or two with runners on with right handed sticks at the plate. He’s clearly shown that he can generate strikeouts against righties and that is one of the more effective ways to kill a rally.

The other factor that makes Romo excellent as a guy to put out spot fires is the fact that he’s fairly good at inducing ground balls. Over his career he’s induced ground balls 35.6% of the time its in play and last season was in-line with that rate (34.9%).


Where the M’s will run into trouble is if Scott Servais has to rely on him for heavy innings usage. The reality is that’s not who he is anymore and if he’s over 50 innings then the M’s could be in a bit of trouble. This is a guy who has the tools to get you out of tight spots in competitive games and that’s how he should be used. Anything else would indicate that there has been a mismanagement of the resources Seattle has in the bullpen.

Afterall, power arms Ken Giles and Andrés Muñoz are expected back this season after missing most of 2021 with surgeries. I don’t have any issues with adding another arm, especially one that generates strikeouts against right handers like Romo does, but he can’t be one of the go to guys in the pen this season…even with Casey Sadler missing the season because of an injury.

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