SEATTLE — As he watched home plate umpire Chad Fairchild signal a swing and strike three Tuesday night, Seattle Mariners starter Luis Castillo walked off the mound and unleashed his customary uppercut fist pump, a move Cincinnati Reds fans saw plenty of when he was with their team.It was Castillo’s 101st pitch of the night in his 122nd start with the Mariners since the Reds sent him westward at the 2022 trade deadline. He’s become a mainstay in Seattle’s deep rotation, helping lead the Mariners to the playoffs twice since arriving.The man on the other end of the strikeout, Reds second baseman Edwin Arroyo, struck out for the 25th time in his big-league career, dropping his average to .243. Arroyo was one of four prospects traded from the Mariners to the Reds four years ago.The Reds were widely praised for their haul at the time. The Athletic’s Jim Bowden gave the Reds an A for their overall trade deadline. Baseball America ranked Noelvi Marte and Arroyo the third- and fourth-best prospects dealt at the deadline. ESPN gave the Mariners a C on the deal and the Reds an A, adding: “They may have hit a home run.”Four years on, the deal was certainly worth it for the Mariners. For the Reds?“I am not sure we actually know,” Cinncinati manager Terry Francona said.Luis Castillo has helped the Mariners to two postseason appearances since being traded from the Reds in 2022. (Steph Chambers / Getty Images)Two of the four players — Arroyo and Marte — were in the lineup for Tuesday’s 4-2 victory over the Mariners. They combined to go 1 for 7 in the game and 1 for 6 against Castillo.The Mariners’ broadcast opened with a graphic comparing Castillo’s 9.1 fWAR to the combined negative-0.8 fWAR of the four prospects the Reds received, including negative marks for both Arroyo and Marte.