While it’s a major blow that Lucas Giolito is likely to be out for at least the entire 2024 season due to a double whammy of elbow injuries, the Red Sox are making efforts to stabilize their already-thin rotation for the longer term. On Thursday, righty Brayan Bello agreed to a six-year, $55 million extension with a $21 million club option for his seventh season. In a well-timed touch, the formal announcement of the deal is expected on Saturday before the Red Sox play the first of two exhibition games against the Rays in Santo Domingo, Dominican Republic, where Bello will be surrounded by family and friends.

The guaranteed portion of Bello’s contract covers the 2024–29 seasons, the last of which would have been his first year of free agent eligibility. The total value of the deal is the second-largest ever for a pre-arbitration pitcher, just surpassing Hunter Greene’s six-year, $53 million extension, which he signed last April with comparable service time and which also includes a club option. Spencer Strider’s similarly structured deal, which came in at $75 million for six years plus a club option, is the record. (Hat tips to ESPN’s McDaniel and the Boston Globe’s Alex Speier for those comps).

The 24-year-old Bello, whom the Red Sox signed out of the Dominican Republic on July 2, 2017 for a bonus of just $28,000, solidified his spot in the majors last year after debuting in mid-2022. Last spring training he was pencilled in as the team’s sixth starter behind Corey Kluber, Nick Pivetta, Chris Sale, James Paxton, and Garrett Whitlock, and he began the season on the injured list recovering from a bout of elbow inflammation. But as injuries and/or ineffectiveness took hold of each member of the planned starting five, he moved up in the pecking order; after making his first start of the year on April 17, he remained in the rotation for the rest of the season, though he was briefly optioned following his second start before an injury to Whitlock brought him back for good. Bello’s 28 starts and 157 innings — the most by a homegrown Red Sox starter since Clay Buchholz in 2014 — both led the staff, while none of the aforementioned five made more than 23 starts or totaled more than 107.2 innings in the rotation.

In terms of run prevention, Bello was unremarkable, with final numbers straddling league average: a 4.24 ERA (93 ERA-) and 4.54 FIP (105 FIP-). However, those numbers are inflated by a pair of bad starts at each end of the season, in which he allowed 20 runs, 10 walks, and six homers across 16.1 innings. Even with his bad season-opening starts against the Angels and Brewers, he was much stronger in the first half than the second, when his home run rate more than doubled and his strikeout and walk rates inched in the wrong directions:

Perhaps not surprisingly given that he set a career high in innings (163, including a rehab start at Triple-A Worcester, up from 154.2 between the majors and minors in 2022), Bello wore down late in the year. Via the Boston Globe’s Julian McWilliams:

Fatigue and heavy legs began to set in. His slider didn’t quite have the sharp break to deter hitters from his two dominant pitches. His four-seam fastball played more as a show-me pitch, but Bello had difficulty locating it above the zone where opponents couldn’t do damage.

While Bello’s sinker/changeup combo turned heads, he’s far from a finished product, as the numbers attest. His sinker, which averaged 95 mph, kept righties at bay (.245 AVG, .381 SLG, 19.3% whiff), but not lefties (.341 AVG, .537 SLG, 8.2% whiff), which helped to account for one of the largest platoon splits for any righty pitcher:

As you can see, this was a particular problem for Red Sox starters, with Houck — who ranked third on the team with 21 starts, helping to fill the void left by so many injuries — having an even larger split than Bello, and Pivetta cracking the top 20, too.

Meanwhile, Bello’s signature changeup befuddled hitters, who managed just a .196 average and .291 slugging percentage against the pitch while whiffing on 38.7% of their swings. Less effective were his slider and four-seamer, with batters posting a .304 AVG and .457 SLG against the former and a .310 AVG and .646 SLG against the latter, which averaged 95.5 mph but just 2,083 rpm, placing him in the fifth percentile for spin rate.

Bello and the Red Sox are quite aware that his arsenal needs refinement, with chief baseball officer Craig Breslow telling reporters on Wednesday, “We still think that his best years are ahead of him. We recognize some opportunities to further optimize the repertoire and we’re super excited about having him.” The pitcher spent the offseason working on elevating his four-seamer above the zone to change the eye level of hitters and get more chases outside the strike zone. He also threw a few sessions under the watchful eye of Hall of Famer and Red Sox special assistant Pedro Martinez, who offered Bello pointers on sharpening his slider with a different grip. To improve his stamina, he worked to strengthen his legs, not that we haven’t heard that one before.

Via Dan Szymborski, here’s a look at Bello’s ZiPS projection percentiles for 2024:

As for the extension, it’s literally pretty much right on the money according to Dan’s model:

The ZiPS contract recommendation for the first six years of that deal is $50 million, so while the Red Sox see him as a potential no. 1 starter, Bello doesn’t have to be much better than average to match that valuation. He could wind up delivering a whole lot more value if he approaches his ceiling, but as a hard-throwing young hurler who’s years away from what he hopes will be his biggest payday, he’s got protection if things go south.

For the Red Sox, this is a positive move following a dreary and disappointing winter. Despite chairman Tom Werner’s assertion that the team would go “full throttle” in its efforts to improve after dismissing chief baseball officer Chaim Bloom, Boston has signed just two free agents to major league deals, Giolito (two years, $38.5 million) and Liam Hendriks (two years, $10 million). The former may be headed for Tommy John surgery, while the latter is expected to miss most or all of the season recovering from his own August 2023 Tommy John procedure. The team did make some trades, most notably dealing away Alex Verdugo, acquiring Tyler O’Neill, and swapping Sale for Vaughn Grissom, but that’s hardly a radical makeover for a team that has missed the playoffs in four of the past five seasons and projects to finish last in the AL East for the third straight year.

What particularly stands out about this Bello move is that the Red Sox have just one other pre-arb or arb-eligible player signed to an extension (Whitlock), which is a rather scathing indictment of their player development pipeline — though they did lock up Rafael Devers last year as he entered his final year of arb eligibility. This is at least a step in the right direction, and hardly an exorbitant amount of money. It won’t hamper them the way that, say, getting 11 starts from Sale from 2020–22 at a cost of about $71 million did. Which isn’t to say that Bello’s going to be as good as Sale, but let’s also remember that the White Sox (and later the Red Sox) got the best years of the wiry lefty’s career under a five-year, $32.5 million extension (2013–17) that had two club options tacked on.

Indeed, the Red Sox’s failure to develop quality homegrown pitching has been a particularly sore spot that has doomed multiple regimes. Again, it had been nine years since a pitcher they produced — as a draft pick or as an international free agent — threw as many innings in a season as Bello did in 2023. If Red Sox are to compete in the AL East while trying to live with midsized payrolls, they need to grow pitchers from within and hope some of them flourish to the point of being worth building around. They believe Bello can be one of them, and well, it’s a start.

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