Bartosz Slisz scored on a header in the 76th minute and visiting Atlanta United completed one of the biggest upsets in MLS Cup Playoff history with a 3-2 win over Lionel Messi’s Inter Miami in the deciding match of their Round 1 tie. series on Saturday nights in Fort Lauderdale, Fla.

Slisz’s goal came as Miami defenseman Tomas Aviles lay on the ground in his own penalty area and his teammates begged referee Lukasz Szpala to stop the play.

But the rules require officials to stop play only if there is suspicion of a head injury and Aviles was clearly grabbing his leg. While Miami appealed, Atlanta played on, with Pedro Amador delivering a sweeping cross from the left and Slisz meeting it and heading emphatically past goalkeeper Drake Callender.

Jamal Thiare scored a first-half brace for ninth-seeded Atlanta, which needed to win its final two regular-season games to reach the Eastern Conference wild-card game.

From there they triumphed on penalties at CF Montreal before sharing the first two games against top-placed Miami, with each home team winning 2-1, before Saturday’s shock away win.

Brad Guzan made seven saves to complete a heroic effort in the best-of-three series and help Atlanta advance in an East bracket where all top three seeds were eliminated.

Atlanta will visit fourth-seeded Orlando City in an Eastern Conference semifinal after the November international break. Messi and Miami are eliminated after scoring an MLS-record 74 points in the regular season, capturing the Supporters’ Shield and topping the playoffs.

Messi scored a second-half equalizer for Miami, his first goal of the postseason and a rare goal through the air after providing an assist in the series-opening win two weekends ago.

Matias Rojas opened the scoring for the Herons in the 17th minute on a rebound after Guzan had saved an earlier Messi attempt.

But Thiare turned an early deficit into an early lead for Atlanta over the next four minutes. In the 19th minute he met Dax McCarty’s deflected ball and hammered a finish past Callender into the top right corner.

Two minutes later, Thiare set up the finish with a clever square pass from Aleksey Miranchuk, after McCarty’s ball from midfield freed Miranchuk down the right.

–Field-level media