What happened: The USMNT wingback is set to reunite with former Columbus Crew teammate Aidan Morris. Sebastian Berhalter, Adilson Malanda and Riley McGree are also part of the English club's squad.
Why it matters: The transfer would give Middlesbrough another player with MLS experience. Columbus would lose a USMNT wingback during the 2026 regular season.
By the numbers: Morris joined in 2024, Malanda arrived in January and Berhalter signed this week.
What to watch: The clubs must complete the deal before Arfsten can join the squad. Columbus' response at wingback bears watching.