Analysis: Ranger Suárez gives the Red Sox a run-prevention ace built for October

What does Ranger Suárez specifically bring to the Red Sox?

While with the Phillies, Suárez established himself as one of the best left-handed starters in the majors, while becoming a fan favorite among Philadelphia’s passionate fan base. Let’s go under the hood and examine the advanced pitching metrics that explain why Boston quickly pivoted to Suárez in free agency.

He won’t bring power pitching as you’ve seen from Garrett Crochet; in fact, he is just the opposite. The southpaw doesn’t win with power; he’s a finesse arm that focuses on limiting damage and putting the baseball on the ground.

Suárez is the definition of a run-prevention pitcher, and his profile translates as such. His value is rooted in consistency spread across his starts. The 30-year-old ranked in the 90th percentile in overall pitching run value, reinforcing that his success with Philadelphia wasn’t luck-driven or situational. His underlying metrics further validate the profile: an 84th-percentile xERA (3.16), 70th-percentile xBA (.226), 95th-percentile average exit velocity allowed (86.5 mph), 89th-percentile barrel rate, and an elite 98th-percentile hard-hit rate suppression.

Suárez’s success and effectiveness came from his secondary pitches. He threw five different pitches—a sinker, four-seamer, cutter, changeup, and curveball—at least 14% of the time in 2025. Yet even his most frequently used pitch, the sinker, accounted for just 28.6% of his overall usage. When facing left-handed hitters, Suárez threw his sinker 45.7% of the time.

The southpaw ranked in the 90th percentile in off-speed run value and the 88th percentile in breaking-ball run value in 2025. His changeup held opponents to a .203 batting average, while his curveball was even more effective, limiting hitters to a .192 average. As his velocity has dipped, Suárez has adapted. His four-seam fastball averaged 91.3 mph in 2025, down from 93.4 mph in 2023, while his sinker dropped from 92.8 mph to 90.1 mph over that same span. 

Velocity has never been his calling card—he ranked just in the 7th percentile in fastball velocity last season—but his fastball still posted a respectable 59th-percentile run value because it plays off his elite secondary mix. Suárez compensates for his lack of velocity with elite command. His 5.8% walk rate in 2025 ranked among the top 20 starters (minimum 150 innings), but his command goes beyond simply limiting free passes. His 22.2 percent whiff rate ranked in the 24th percentile, but hitters chased pitches outside the zone at a 78th-percentile rate, often producing weak contact rather than strikeouts. He paired a league-average strikeout rate (55th percentile) with elite control (86th-percentile walk rate), reinforcing his identity as a strike-thrower who avoids walks.

That approach plays directly into his biggest strength: keeping the ball on the ground. Suárez posted a 48 percent ground-ball rate, ranking in the 76th percentile, and when combined with his elite exit-velocity suppression, it allowed him to limit big innings despite modest strikeout totals. For Boston, aligning him with an above-average defense will be key to maximizing his value.

With the current infield alignment of Willson Contreras at first base, the possibility of Marcelo Mayer at either second base or third base, depending on how the remainder of the offseason unfolds, and Trevor Story at shortstop, Boston’s infield remains incomplete behind one of the game’s best ground-ball pitchers.

Suárez's ability to limit