Birmingham City F.C. have signed defender Kai Wagner from Philadelphia Union in a transfer deal. Wagner, 28, joins the Blues in the midst of their 2025-26 EFL Championship season, sitting at 14th in the table. The left back has established himself as one of Major League Soccer's top left backs since joining the league in 2019. He holds the club record for regular season assists with 56, surpassing Sebastien Le Toux's previous record when he notched his 51st assist on September 28, 2024. With eight career goals, 204 games played (198 starts) and 17,785 minutes logged, Wagner has been a stalwart of the Union's backline, helping the team secure two Supporters' Shields and making six playoff appearances, including an MLS Cup Final. Individually, Wagner is a three-time MLS All-Star and two-time MLS Best XI selection. Prior to joining the Union, Wagner came from German side Würzburger Kickers. The Blues have earned major honors in their history, including two League Cup titles, and were recently promoted from League One to The Championship at the end of the 2024-25 season.