One of MLS' most promising young attacking playmakers faces one of the league's best midfield destroyers when Brenden Aaronson's Philadelphia Union play Diego Chara's Portland Timbers in the MLS is Back tournament's semifinals Wednesday night near Orlando.

The 19-year-old Aaronson has been the center of the attack on the field -- and the center of attention off of it -- for the Union, who came into the tournament among the favorites, according to several oddsmakers.

With reports swirling of an imminent move to Europe, Aaronson has two assists in the competition, including the diagonal ball that freed Sergio Santos for his second goal - and Philadelphia's third overall - in a 3-1 quarterfinal victory over Sporting Kansas City.

"I thought he was dominant, he was active. His movement off the ball to find space was really good," coach Jim Curtin said of Aaronson's performance last Thursday. "The ball he plays on the third goal is a top ball in any league - in the leagues in Europe, that's a pass that not many people see. His confidence is very high right now."

Trying to replicate that same level of play against Chara is an added challenge, however. The holding midfielder is arguably as important to his team as any player in MLS. The Timbers went four years without a regular-season win when Chara did not play, a streak that began in 2015 and ended with a 4-0 victory over the LA Galaxy last year.

The first game in that streak? Portland's last loss to Philadelphia. The Timbers have won four straight in the regular season series.

The Timbers have their own reliable offensive weapons in the veteran Argentine duo of Sebastian Blanco and Diego Valeri. At age 34, Valeri is not always a 90-minute player, but Blanco, 32, has transitioned into Valeri's old role as the centerpiece.

Blanco has two goals and five assists in the tournament, and has been involved in all but three of the Timbers' 10 goals.

"We know what we have in him," Timbers coach Giovanni Savarese said. "He shows that every single practice, every single day when he's with us. This year, his mind is clear. He's doing an excellent job, and you need players like him."