Ahead of the 2026 MLB Trade Deadline, former Toronto Blue Jays reliever Seranthony Dominguez was traded by the Chicago White Sox to the Seattle Mariners. He was one of the pieces the White Sox flipped to land star pitcher Luis Castillo from the Mariners.
Seeing the White Sox decide to move on from Dominguez was not necessarily surprising. The 6-foot-1 righty struggled to find his rhythm with the White Sox this season, as he had a 3.99 ERA in 43 appearances. Overall, he was having trouble living up to the two-year, $20 million contract he signed with the White Sox during last offseason.
Dominguez will be looking to regain the form he had with the Blue Jays last season now that he has gotten a fresh start with the Mariners. Unfortunately for him, his tenure with the Mariners has gotten off to a terrible start.
Dominguez made his debut for the Mariners earlier this week against the Detroit Tigers, and it could not have gone much worse for the former Blue Jays reliever. In 0.1 innings pitched, he allowed two walks, two home runs, four hits, and four earned runs. With that, there is no question that he had a debut to forget with the Mariners.
Seranthony Dominguez’s first game with the Mariners.
— Mike (@ChiSoxFanMike) August 5, 2026
0.1 IP, 4 H, 4 ER, 2 BB, 0 K
2 home runs allowed. pic.twitter.com/LNFaLUZWC5
However, Dominguez will now need to move on from this rough performance and try to turn things around with the Mariners from here.
Why former Blue Jays' Dominguez could heat back up
When looking at how effective Dominguez was just last season for the Blue Jays, there is reason to believe that he can get things back on track with the Mariners. In 24 regular season appearances with the Blue Jays last season after being acquired from the Baltimore Orioles, he posted a 2-1 record, a 3.00 ERA, and 25 strikeouts. He also posted a 2-0 record, a 3.18 ERA, and 10 strikeouts in 12 appearances for the Blue Jays during their playoff run last year.
If Dominguez can regain this form during the final stretch of the season, it would be good news for the Mariners. Keep in mind, the Mariners are currently three games behind the Houston Astros for the top spot in the American League West and are looking to climb up the standings.
Nevertheless, it will be interesting to see if Dominguez can bounce back from his ugly Mariners debut from here.
