Red Sox Find Their Shortstop, Trade For Adalberto Mondesi

Peter Aiken-USA TODAY Sports

The Red Sox have spent most of the offseason with a big hole up the middle of their infield. With Xander Bogaerts departing in free agency, Boston had no true shortstop on the roster. While Enrique Hernández and Christian Arroyo each made a handful of starts at six on Bogaerts’ off days, neither is a true shortstop and both are needed to man the other up-the-middle positions, where the team still lacks depth. Yesterday, the Red Sox at least partially filled that hole, trading a left-handed reliever Josh Taylor to the Royals for a switch-hitting infielder Adalberto Mondesi and a player to be named later.

A healthy Mondesi is one of baseball’s most exciting position players to watch. Most fans probably know him for his top-of-the-charts speed, which he shows off in all facets of his game. Let’s start with the most visible one: baserunning. Mondesi has multiple seasons under his belt with an average sprint speed above 30 feet per second, making him one of the most electric runners in the game. Since his debut in 2016, 44% of his competitive runs have been defined as bolts, a mark bested by just four others during that time. Of course, Mondesi has also used his speed to steal bases, and his combination of aggressiveness and efficiency has allowed him to put up ludicrous stolen base numbers despite never getting a full season’s worth of plate appearances:

Plate Appearances Per Stolen Base Leaders, 2018-22

SOURCE: Baseball-Reference

min. 1000 pa

Over the past five seasons, Mondesi is fourth in total steals, and when you account for the fact that he’s played in far fewer games than the rest of the pack, he blows everyone else out of the water. And he’s done this despite having far fewer opportunities to steal even when he’s playing. See, Mondesi swings at everything, and not in the Vladimir Guerrero way where he could bloop a single against a pitch in the dirt. Mondesi chases about 40% of pitches off the plate, comes up empty on over a third of his swings, and walks just 4.4% of the time. His .289 OBP ranks near the bottom of the leaderboards, and the only other player who has similar stolen base numbers with equal levels of on-base futility, Hamilton, had the benefit of 58 pinch-running appearances to boost his steal totals; Mondesi has just three. In 2019, he played just 102 games, but stole 43 bases despite an OBP of just .291, including a dozen steals of third, five more than the next-best finisher.

While Mondesi has similar stolen base numbers to other speedsters like Smith and Berti, the shape of his offensive performance is quite different. Most hitters who rely on speed for success like to pound the ball into the ground and let their legs carry them down the line – Smith and Berti each hit about twice as many groundballs as fly balls. Mondesi, on the other hand, has a more modern batted ball profile, hitting grounders and fly balls in more equal proportion while posting an above-average pull rate. Sometimes this works well, like in 2018 when he slugged .498 and played at a 5.2 WAR per 600 PA pace. But he often struggles with barrel accuracy, as evidenced by his poor line drive and pop up rates. And like most hitters with approach issues, his offensive performance can tank quickly when the balls stop dropping for hits. With a strikeout rate so high, Mondesi often doesn’t give himself the chance to use his speed and baserunning skills, instead taking a slow stroll back to the dugout. This is why, despite plus raw power and elite speed, his career wRC+ sits at a pedestrian 79.

Mondesi’s outlier speed also makes him a plus defender all over the infield. His near-limitless range combined with solid hands and actions has allowed him to not only get more grounders than most others, but to also convert those plays into outs. Statcast’s defensive metrics consider him stellar, averaging +12 RAA per 1,500 innings, functionally contributing over a full win per season with just his glove. He’s also been above average in limited reps at both second and third base, allowing him to serve in a utility role if the Red Sox find other options at shortstop. Mondesi’s presence provides a major boost to Boston’s infield defense as a whole, as he replaces Bogaerts, who was worth -26 RAA and -50 DRS during his time there. Combined with left-side partner Rafael Devers (-11 RAA, -44 DRS), the Red Sox defense has produced the fifth largest difference between actual and expected batting average on groundballs in the majors during the Statcast era. And with Devers sticking around for the foreseeable future, Mondesi’s slick glove work will anchor their left side, at least for now.

But while Mondesi is a serviceable player due to his baserunning and defensive skills at shortstop, he also has a significant injury history that has cost him much of the past half-decade. He missed half of 2018 with a shoulder impingement, then was sidelined for two months in ’19 with shoulder and groin issues. His only full season occurred during the shortened 2020 campaign, but he has appeared in just 50 games since then. He suffered oblique and hamstring injuries in 2021 and saw his ’22 season end just a few weeks after it began due to an ACL tear. Indeed, he is still rehabbing back from that injury, and his availability for Opening Day is not assured. It would be foolish for the Red Sox to pencil him in for 150-plus starts, both due to injury risk and the lackluster quality of his bat. Absent other additions, Hernández seems like the best bet to take over at shortstop if Mondesi is out, especially with the addition of Adam Duvall, who projects well in center field despite playing in a corner for most of his career. And while Trevor Story might be back later in the season, his elbow injuries may prevent him from returning to shortstop, as evidenced by his eighth-percentile arm strength and significant improvements in OAA after moving from shortstop to second base.

Headed to Kansas City in exchange for Mondesi is Josh Taylor. Like Mondesi, Taylor missed nearly all of 2022, only appearing in minor league rehab games before being shut down for the season with a lingering back issue. When healthy, Taylor almost exactly defines the “95 and a slider” relief archetype, throwing fastballs and sliders each about half the time, with the heaters averaging 94.6 mph. Like many other middle relievers, Taylor has an excellent career strikeout rate (29.4%) but is also occasionally prone to wildness, walking 10% of hitters. In about 100 career innings, he has a 79 ERA- and 75 FIP-, making him solidly above average when available.

This trade, along with the deal that sent Michael A. Taylor to Minnesota in exchange for sidewinding lefty Evan Sisk and flamethrower Steven Cruzsupplements the pitching depth of a farm system that hasn’t reached its desired developmental outcomes recently. The Royals system has been much maligned for its struggles getting numerous big-name pitching prospects to pan out as major league starters. As for relievers, just two of the eight arms projected to make their bullpen this season were originally drafted or signed by Kansas City; the rest were acquired via free agency or trade. Perhaps the Royals are hoping for solid major league outcomes from younger pitchers who have already had much of their developmental work done by other teams. Taylor immediately slots into a bullpen that finished 27th in relief ERA (and starter ERA) last season, while Sisk and Cruz build depth for the future.

I think the Red Sox will end up getting the upper hand in this trade. While Mondesi is in his last year of arbitration, and his median projection for plate appearances is probably in the 300s, Taylor doesn’t move the needle at all for a team that lost 97 games last year and whose biggest offseason upgrades have been Jordan Lyles and Ryan Yarbrough – two players who will serve a bigger role in allowing the Royals’ other starters to develop than contributing to wins. Taylor isn’t a bad pitcher, but he almost certainly won’t be a member of the next competitive Royals team. It’s possible that he can be traded for prospects down the line, but they could have done the same with Mondesi, possibly without sacrificing another prospect like the PTBNL. The Red Sox, who’ve already signed a solid relief duo in Kenley Jansen and Chris Martinare left with just one left-handed reliever, a groundball specialist Joely Rodríguez. But with the ‘pen already bolstered and their shortstop issue far more difficult to solve in the free agent market, the Red Sox seized the opportunity to try to patch their biggest hole.

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