Currently in first place in the American League Central, the Chicago White Sox struck early in the arms race, making a significant trade with the Seattle Mariners. Running out of time before the August 3rd trade deadline, Chicago made its first move, addressing their need for an innings eater in the pitching rotation. Making a run at their first division title since 2021, the White Sox gave up a significant return for starting pitcher Luis Castillo. Chicago parted with a relief pitcher, outfield depth, and a top prospect. Here are the grades for each team involved in the trade.
Entering the final days before the trade deadline, Chicago identified a desperate need for a starting pitcher capable of making it through a lot of innings. So far in 2026, the White Sox have had only two starting pitching performances go at least seven innings, and their starting pitchers average only 4.29 innings per start. While they reportedly spoke to several teams about starting pitchers, Chicago landed on starter Castillo from the Mariners.
Now in his 11th season in the majors, Castillo moves to his third team with the White Sox. Historically a reliable top-end starter, he has struggled this season, currently sporting a 5.06 ERA. The high ERA comes with a 3-9 record in 20 games pitched with 17 starts over 99.2 innings, averaging 4.98 innings per game. The 2025 season treated Castillo much better, as he posted an 11-8 record with a 3.54 ERA over 32 starts and 180.2 innings.
Now that Castillo is on the White Sox, the team hopes the change of scenery will bring him back in line with his previous season’s stats. Manager Will Venable has confirmed that Castillo will slot right into the rotation, sending starter Erick Fedde to the bullpen. The move allows more flexibility should any starter need to be pulled early in games. Chicago will also absorb the remainder of his 2026 salary and will owe Castillo $25 million in 2027.
Chicago White Sox Grade: B+
Presently just outside the playoff picture, the Mariners decided to trade one of their veteran pitchers. The return received from Chicago was hefty, considering Castillo was not one of the several rumored players Seattle was shopping at the deadline. While they only got one prospect in the deal, the Mariners added reliever depth and a major league outfielder.
Being added to the Seattle bullpen is relief pitcher Seranthony Domínguez. In 2026, the 31-year-old has a 4-3 record in 43 games pitched with a 3.99 earned run average. A ten-year veteran, he has pitched 38.1 innings so far, with 47 strikeouts to 23 walks. Much like the traded Castillo, Domínguez is under contract through the 2027 season, giving the Mariners a controllable reliever.
Another player sent to Seattle, outfielder Nolan Jones, was playing in AAA with the White Sox organization. The 28-year-old has spent time in the majors with Cleveland and Colorado, and profiles as a backup option or injury replacement. In 2023, Jones had his best season, hitting 20 home runs for the Rockies with 62 runs batted in while batting .297 in 106 games. Unfortunately for him, Jones has not been able to replicate those numbers in the majors.
The highlight of the trade for the Mariners comes in the form of catching prospect Boston Smith. The former 2025 sixth-round draft pick from the Washington Nationals was ranked as the 15th top prospect in the Chicago minor league system. Across A and AA in 2026, Smith has hit 22 home runs, driven in 58 runs, and stolen 10 bases, all while batting .291 this season. While he is still developing, Seattle fans can expect to see him debut late 2027 or early 2028 on his current pace.
Seattle Mariners Grade: B
Looking at the trade on its face, both teams appear in a position to benefit from the pieces involved. The Chicago White Sox received a controllable starting pitcher who can eat innings and give the bullpen some much-needed relief. The Mariners received a controllable bullpen piece, outfield depth, and a potential future starting catcher, allowing Seattle to move Cal Raleigh to designated hitter. For those reasons, both teams deserved a grade in the B range.
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