CHESTER, Pa. -- Jesús Bueno scored the decisive goal in a penalty shootout after the Philadelphia Union blew a two-goal lead late and the top-seeded Union beat the Chicago Fire FC on Sunday in a best-of-three first-round opener of the MLS Cup playoffs.

Chicago goalkeeper Chris Brady had a save on a shot by Mikael Uhre as the match moved directly to PKs after a 2-2 draw in regulation, but Andre Blake answered on a shot by former teammate Jack Elliott.

Francis Westfield and Milan Iloski had goals for Philadelphia in the next two rounds, while Brian Gutiérrez and Hugo Cuypers scored for Chicago. Tai Baribo gave the Union a 5-4 lead and Bueno drilled the winner after Joel Waterman clanked his shot off the crossbar.

Indiana Vassilev got assists from Uhre and Iloski to find the net in the 70th minute for a 1-0 lead. Vassilev is in the postseason for the first time after coming over in a February trade with St. Louis City. Uhre, who subbed in for Bruno Damiani in the 64th minute, collected his first assist in his seventh playoff appearance.

Iloski took a pass from Baribo and scored five minutes later for a two-goal advantage. Both players were making their postseason debuts.

Jonathan Bamba cut it to 2-1 with his first postseason goal in the 84th minute of his second playoff appearance. Defender Andrew Gutman notched his first assist in three playoff appearances.

Elliott scored in the third minute of stoppage time with a swerving strike from distance to tie it. It was his first postseason goal for the Fire after scoring three times in 11 playoff appearances over six seasons with the Union.

Sergio Oregel was tagged with a straight red card for a foul on Baribo a minute later, forcing Chicago to play a man down over the final five minutes of stoppage time.

Blake finished with three saves in goal for the Union, who won the Eastern Conference and Supporters' Shield this season. Blake allowed 20 goals in 13 prior postseason starts for the Union dating to 2016.

Philadelphia has made the postseason in seven of the last eight seasons and nine overall.

Chris Brady didn't have a save in regulation in his second playoff start for the Fire, who are in the postseason for the 14th time and first since 2017.

The series shifts to Chicago on Saturday.