The Chicago White Sox traded reliever Seranthony Dominguez, outfielder Nolan Jones, and catcher Boston Smith to the Seattle Mariners in exchange for right-hander Luis Castillo, according to Jeff Passan of ESPN. Dominguez signed a two-year, $20 million contract with the White Sox this offseason to be the team's closer. He struggled as the team's closer earlier in the season, converting just 12 of 17 save opportunities and eventually lost the job to Grant Taylor and Sean Newcomb in June. The 31-year-old owns a 3.99 ERA, 1.33 WHIP, and 47 strikeouts across 38 1/3 innings. With Andres Munoz locked in as Seattle's closer, Dominguez will be used mostly in leverage situations. Fantasy managers can move on from Dominguez outside leagues that reward saves and holds, as he is third in the pecking order for save chances behind Munoz and Jose A. Ferrer.

Seattle Mariners top pitching prospect Kade Anderson should be on the radar of all fantasy managers heading into Week 19. On Saturday, the Mariners traded veteran right-handed pitcher Luis Castillo to the Chicago White Sox per ESPN's Jeff Passan. This move opens a role in their starting rotation for a potential sixth man. While Emerson Hancock currently occupies the No. 5 spot in the rotation, he has also been linked to many trade rumors, which would create an even clearer path for the team's No. 1 prospect to play a major role over the final stretch. Anderson has been knocking on the MLB door since making his pro debut in 2026. Through his first 16 starts at Double-A (82 1/3 innings), the southpaw has posted a dominant 1.20 ERA, 0.66 WHIP, and a 119:12 K:BB. Even if the Mariners were to hold Hancock through the deadline, Anderson could find a role as a sixth man in the staff. If Hancock were to move to a new club, the budding southpaw could earn the call immediately after. He is a priority stash target across all formats as he would hold must-start upside on a per-start basis.

Right-handed pitching prospect Brady Smith is set to join the Detroit Tigers, according to Jeff Passan of ESPN, in the deal that sent Tarik Skubal to the two-time reigning World Series Champions. Smith was viewed as the No. 29 prospect in the Dodgers system prior to the deal. While Zyhir Hope and River Ryan are viewed as the headliners in this deal, Smith has shown high-end strikeout upside in the lower levels and could be worth close monitoring in deeper dynasty leagues. He began the 2026 season at the Low-A level, where he racked up an impressive 104 strikeouts over only 65 innings of work with a 3.88 ERA. However, since moving up to High-A (9 1/3 innings), Smith has allowed eight runs and totaled just nine punchouts. While the right-hander will need some time as he progresses through the minor leagues, his strikeout potential makes him worth following for the remainder of the second half.

The Los Angeles Dodgers traded outfielder prospect Zyhir Hope as the headliner in the deal that brought them left-handed pitcher Tarik Skubal on Saturday evening, according to Jeff Passan of ESPN. Hope was viewed as the No. 3-ranked prospect in the Dodgers system before the trade and sits as the No. 19 overall prospect in the sport on MLB Pipeline. Alongside Hope, the Dodgers traded right-handed pitchers River Ryan and Brady Smith. Hope has spent the entire 2026 season at the Double-A level and looked comfortable. Through 94 games at Tulsa, the budding star has posted a dominant .293/.363/.530 line with a .899 OPS, 17 doubles, 23 home runs, and 18 stolen bases. Fantasy managers should keep a close eye on his status as a late-season promotion to Triple-A Toledo is likely in play given how comfortable he has looked at Double-A. He is expected to compete for a 2027 MLB debut.