Free Agent Folder #3: Sergio Romo

Alessandro Zilio
10 min readJan 14, 2022


We are little more than a month away from pitchers and catchers reporting, a signal that Spring Training is near and baseball is going to wither away every single minute of my life for half a year or so. We are also in the midst of a lockout, both sides anchored to their requests and no agreement in sight so there’s that.

The only baseball news going around nowadays are a young woman breaking barriers in Australia, with mid 80s gas and a yacker curve and not a gimmick knuckler as in Pitch, and players hanging their cleats, club legends as Kyle Seager and human curse breaker Jon Lester the latest to abandon the mound for a much deserved buen retiro.

Still, we are going to play one day right?! Therefore let’s be smart about it and not be caught unprepared when it comes to building a WS-worthy roster: welcome to another entry of my Free Agent Folder, my not-so-secret research on third string FA options that might be exactly what your team needs, and cheap to sign no less!

I’m not an advocate of spending money on a bullpen: the nature of a reliever is riddled by variance, such that every year a well known late inning weapon seems to falter out of nowhere and equally as unexpectedly a raggedy journeyman or no-name NRI becomes a lockdown fireman. There’s no such thing as a bad 1 year deal though and that’s what I’m all for when searching for relief pitching: a short term gamble on a mistery box is calculated risk, a 4-year $10M+ AAV contract for a RP is changing your salary in coins and trying your luck at the slots.

There’s something to be said though: as the season progresses and October gets closer, starters tend to fall out of fashion, pulled at the first pressure situation in favor of a series of middle relief options that have to pass the baton to the hopefully premium setup/closer combination, so inking a strikeout machine, damage suppressor included, makes perfect sense, even if that machine has an inherent risk of failure.

In that spirit, do you know that one of the most historic, widely known and beloved relievers in the last decade could suit up for your team and helm a nice 7th inning spot, without asking for much and bringing rare consistency and all the experience of a 38 y.o. baseball jokester?

Still going strong, Sergio Romo!

Why buying?

- He nullifies hard contact by design

Romo, along the likes of other proven middle relief stalwarts a la Joakim Soria/Craig Stammen, built his career on disrupting contact to soft bits, relying far more on deception and location than pure stuff and strikeouts:

Throwing his patended sweeping slider more than 50% of times and complementing it with an 85 mph sinker and a changeup, he commands both sides of the plate getting more called strikes (19%) than swinging ones (12%), a 31% CSW that is above average even in the world of fireballing relievers with disgusting breaking balls.

His sidearming delivery, a long arm action with the occasional quick pitch and timing disruption, makes for an uncomfortable AB especially for RHB and his sinker/slider sideways combo, both lulling to sleep the batter due to their lack of speed, is and has always been tough to square up: since Statcast’s inception in 2015, Romo reigned in the 98–100th percentile in avgEV and HardHit%, in 2021 only bested by now Ray and former Astros legend Brooks Raley.

- His secondary pitches are actually pretty good

If his slider is a normal RP’s fastball in terms of usage, his sinker is now what a breaking ball serves as, his preferred secondary with a 30% Pitch% that is 3x what he used to throw in the past: Romo fell in love with the sinking fastball, a nostalgic wise man he all but shelved his brutal 4-seamer, routinely over .400 xwOBA, relying on the east/west effect to do the trick, and results followed.

His sinker, slow but tunneling nicely with his bread and butter slider, allowed a meager .290 xwOBA with an unusual 21% Whiff for such a pitch, a feat of surprise as batters were caught guessing the sweeper so that 85 seemed like 105 tailing back into the zone.

Interestingly enough, his best pitch in 2021 was a seldom used changeup, a 10% usage he ought to increase as he was able to keep LHB to a 1.15 WHIP more due to walks than any other kind of damage.

His cambio makes for one of the strangest pairings in all of baseball together with his sinker: they are almost the same pitch both in hmov and vmov, with the changeup fading a ton but only a 5 mph differential separating the two, and Romo rarely throws it in the zone but man, it’s working wonders!

A 40% Whiff is elite, Luis Castillo territory for a changeup and batters were pathetic against it to say the least: .137/.159/.133 on the xBA/xSLG/xwOBA slashline is the definition of embarassing the opposition. He reserved all but 9 changeups to lefties, allowing a sole double, five singles and nothing else, nada de nada, for the season: long gone are the days of Romo as a RHB specialist, with this dandy of a pitch he may actually be better in the unfavorable matchup than the same-handed one!

- He’s been there, done that and done it again

Romo’s consistency as a reliever is something to marvel at: in his long career he rarely saw his ERA go over 4, hovering around the 3–3.5 range wherever he played, team and inning-wise. From his legendary seasons in SF, a part of one of the best bullpens in recent memory, that of Javier Lopez and Jeremy Affeldt as LH specialists, to stints in Minnesota and Oakland, he survived the test of time, punching his 60+ G ticket, rare stints in the IL/DL and a presence on and off the mound as few others.

On paper his 2021 looks kind the end of the road: 4.67 ERA, a WHIP over 1.2 and more HR than you’d like…but he was also unlucky and deserved better! His LOB% was less than 70%, almost 10 points under his career average, and while a .281 BABIP doesn’t scream fatality, his expected metrics point to another solid season under his belt: a 3.47 xERA is great, even if xFIP doesn’t love his flyball tendencies.

Even as his career approaches the end, he still has quite a few appearances to give, more weak flyballs, the occasional bomb, a deluge of sliders sweeping away and the always stingy sinker down the middle freezing the batter. And if your team’ll ever end up in the Postseason, fear not: Romo is as solid as always even under the bright lights, a career 2.88 ERA from September on and a moment of greatness or two in big spots, shades of Miguel Cabrera looking at one of those sinkers to close a WS.

Why not buying?

- His control is fading

A location-based pitcher, Romo needs to paint corners and work in and out with his slider and sinker crossing up the batter as they approach the plate. That said he also needs to establish the plate early and often, control the AB and get to a 2 strike count to deploy his sweeper effectively:

A sub 60% 1st Pitch Strike rate is strictly related to a BB% over 8%: in 2021 Romo had a hard time starting the count 0–1 as his surefire backdoor slider started to fail him. Batters caught up to it soon, and the Mexican attained a career low in both Swing and Chase rates, less Whiffs and pitches on the Edge, Shadow zone of the plate, resulting in more offerings in the zone and a 7%+ Barrel that is only league average.

Without high octane at disposal to bail him out when his command falters, Romo needs to start each at bat with the right foot, a strike by all means, and put himself in a situation where the batter can’t just sit middle-in on his slow sinker, ditching his low Zone% slider entirely: keep them honest and let the guy at the plate guess wrong.

- His spin rates are down

Not implying anything, but all of Romo’s pitches saw an average 100 rpm decrease from 2020 to 2021, and a lot of that after the sticky substances ban. This is crucial for his slider, that lost 2 inches of horizontal break: never much of a dropper if not a pure sweeping pitch, those few centimeters less may seem nothing but they are the difference between a painted low-away slider and a hanging demolition ball.

The problem with losing movement is not that the pitch loses in quality, rather that the pitcher has to acknowledge it and aim accordingly: keeping sights, delivery and arm action the same, the lack of rpms, and hmov with it, keeps the ball in the zone and as good of a pitch Romo’s slider is, it’s a 77 mph slow bender that has to be placed with caution to avoid it being sent to the stratosphere.

If the spin loss persists, Romo will have to look out and exacerbate his pitch location and sweep. Less Barrels and more walks is not that bad of a deal in the end.

Everyone and his mother needs bullpen help so this is a tough prediction to begin with.

Even with only a couple of seasons left, probably, Romo is still a solid player that fits a wide range of roles: he can be a middle relief option in a quality pen or a late inning weapon too, sometimes trying to bring his own demise with a walk or two, the Fernando Rodney experience, but a lot of meddle and no particular splits to be aware of.

There are teams who like to pick old relief arms, stockpile and either see if they stick or trade them to teams in need: Oakland, Romo’s last home, is widely known to spend his few coins in the pen without focusing on high K% but more on relievers allowing the worst contact profile, Soria and perennial Yusmeiro Petit the examples; Kansas City loves his old bullpen folks, from his legendary Herrera/Davis/Holland winning trio they tried to bring back to the Ian Kennedy resurgence; Colorado famously wasted a ton of $ in building a “super-pen” and with their renewed FO I wouldn’t put past them another try.

There’s a team that seem to have already started the “sign to trade” bullpen plan though, and I bet they’ll add Romo to it: earlier on, the old times when players could be signed to deals and whatnot, the Arizona Diamondbacks inked proven closer Mark Melancon, a master of poor contact himself, to a 2 year $7M AAV contract.

It’s not astounding in terms of money and length, but do the Dbacks need a closer?! Not really, not as much as a couple of bats, an entire rotation and a healthy Ketel Marte, but this was not the point of such a transaction: if somehow Arizona is in the playoff hunt next season, Melancon is as solid as a closer can be and that is a pressing factor come late August; if not, he’s bound to be average at worst but a premium commodity nevertheless, playoff experience and all, a valuable trade chip that could bring Arizona a decent prospect or two.

The same applies to Romo: for a deceptive, funky and flamboyant reliever age is just a number. His stuff has only slightly got worse, he needs to tweak his arsenal adding more changeups and fixing his slider location but even last year’s disappointing results hid much better expectations behind the curtains.

For that I think the Dbacks will give him a 1 year $3–4M deal and slot him in the 6–7th inning, with him, Noe Ramirez and JB Wendelken bridging to Melancon, not an amazing unit but a solid group of relievers with a common denominator: they might not light up the radar gun, but squaring them up is always a hard task.

Will he end the season in Arizona though? Probably not, but don’t be surprised if he’ll resurface in October, late in a meaningful game, locking up your favorite team’s slugger with a sinker right down the pipe after a collection of sliders. That’s what he does.

All graphs and stats from Baseball Savant.



Alessandro Zilio

Italian baseball stathead. I’ll write about MLB, NPB and Korean dramas. A lot of Astros related content and obscure references.