The Chicago White Sox are surprise contenders this year, just a season removed from a 102-loss year and after that awful 121-loss season in 2024. And now? They're acting like a contender at the MLB trade deadline.On Saturday night, with the team leading the AL Central, the White Sox acquired veteran starting pitcher Luis Castillo, a move that will bolster a rotation that's good but could use a real front-line vet like Castillo. And as for the Seattle Mariners, who dealt the 33-year-old hurler with a 5.06 ERA this year? They're still contending in the AL West and maybe they can afford to lose Castillo.So who won this deal? What are the details? As always, we're handing out some grades. Let's break it all down for you:Mariners and White Sox trade detailsWhite Sox get: RHP Luis CastilloMariners get: RHP Seranthony Dominguez, OF Nolan Jones and C Boston SmithWhite Sox trade gradeI dig this move a lot. Castillo isn't having the best of years, but he brings veteran savvy and perhaps a change of scenery will bring him back to his reliable sub-4.00 ERA self. The White Sox didn't give up a ton here, either. It's a good sign for their fans that the franchise is making a move like this after all those triple-digit loss seasons. GRADE: B+Mariners trade gradeThe Mariners' starting pitching depth is sooooo good with Logan Gilbert, Bryan Woo, George Kirby and Bryce Miller. Getting back a reliever who's been pretty reliable in Dominguez is good. Shedding Castillo's expensive contract is also a win. Smith is ranked as Chicago's 15th best prospect on MLB.com, so it's not about getting a young stud. And Jones? He once went 20-20 with a .297 average in 2023, but hasn't done much since. Not a bad deal for Castillo, but we'll see if the bullpen addition helps down the stretch. GRADE: BThis article originally appeared on For The Win: Luis Castillo trade grades: Who won White Sox and Mariners deal?