Aaronson is the subject of widespread interest from Europe. MLSsoccer.com can confirm reports linking Hoffenheim, SC Freiburg and Eintracht Frankfurt with the player, per Bild, ESPN's Taylor Twellman, SportsBuzzer and others.
MLSsoccer.com can add, per a source, that Scottish giants Celtic and an unnamed Belgian club are also interested in acquiring Aaronson.
Aaronson, 19, is a Philly academy graduate who broke through into the first team in 2019 when he made 25 starts for the Union. He earned his first call-up to the senior US national team in October. This season he has picked up right where he left off, with a goal and two assists across five starts.
A modern midfielder, Aaronson has thrived in the Union's high-pressing system. Bild dubbed Aaronson as the "US Kai Havertz", referring to the highly-rated German star who is reported to be closing in on a big-money transfer from Bayer Leverkusen to Chelsea.
Matt Doyle breaks down Aaronson's impact further:
Union head coach Jim Curtin recently discussed Aaronson's rise and laid out his next steps.
"Overall we've challenged him from last season... to get better at making the final ball, to get more goal-dangerous," Curtin said after Philly's win over Inter Miami. "And he's really taken the next step. Everybody sees his work rate and ability to run and cover ground and cover distance. If he's going to make it as a No. 10 at the very highest level, and that's the ultimate goal for him, he's going to do it by being a volume player, a player that's on the ball all the time.
"And he might make a mistake 3-4 times but he's coming again at full speed. So that's something he's worked hard on: His final pass, his through balls, getting his shot off a little quicker in and around the box. He's taken big strides, but the Philadelphia Union, we're going to be greedy and push and demand more of him because he can play even better than he did tonight.
"We're going to continue to push Brenden because we see how much talent he has."