Atlanta United FC finished a whopping 34 points behind Lionel Messi and star-studded Inter Miami CF during the regular season.
Now, the Five Stripes have a shot at pulling off a stunning upset of the best team in Major League Soccer.
Xande Silva scored with about a minute to go in stoppage time shortly after a goal by Messi was waved off by a clear offside, giving ninth-seeded United a 2-1 victory over Miami on Saturday night to even the best-of-three first-round MLS playoff series at one game apiece.
"We've been the so-called underdogs every week," said Derrick Williams, who scored Atlanta's first goal. "We're in fight-or-flight mode, and we're definitely fighting."
United had to pull out a wild-card victory at Montreal on penalty kicks just to get a shot at the Supporters' Shield winner, which set an MLS regular-season record with 74 points.
United finished with just 40 points -- the fewest of any playoff team -- and didn't earn its postseason spot until the final day of the regular season.
None of that mattered when Silva blasted a right-footed shot into the top left corner to beat goalkeeper Drake Callender in the 94th minute.
The Atlanta player celebrated by ripping off his shirt and dancing in front of the supporters section at Mercedes-Benz Stadium while the announced crowd of 68,455 cheered.
Messi had plenty of good scoring chances but only found the back of the net with the flag raised for offside. Atlanta United took off the other way for Silva's game winner.
Miami coach Gerardo "Tata" Martino, though, insisted he was happy with the team's performance, despite the result.
"I am very satisfied with what they did beyond the fact that we are very frustrated with the final result and we have to try to do the same in the third game," he told reporters in a news conference.
Martino brought on attacking players Leonardo Campana and Matías Rojas in an attempt to win the game and the series before it would go to a penalty shootout but it was Atlanta that took advantage of the end-to-end finale.
"It seems to me that we did a lot of good work to be able to win the game," Martino added. "Even in the last 10 minutes we decided to go after them with four attackers.
"We were optimistic even going to penalties because of the very good performers who would have remained on the field if we had finished 1-1. Beyond that the search was to try to win it in the 90 minutes."
United rallied from a 1-0 halftime deficit, the result of a huge error by keeper Brad Guzan, to force a decisive game next Saturday night in South Florida.
Williams tied the match in the 58th minute after a corner kick was turned away by the Herons. Pedro Amador sent a cross back into the box from long range and Williams dove to get a head on it, skipping it past Callender.
Messi misfired on at least three shots, going wide a couple of times before blasting one over the net in the 83rd with Miami pressing for the go-ahead goal. He walked away rubbing his beard, clearly frustrated at his lack of accuracy.
"Keeping him quiet is massive," Williams said. "He's the best player to ever play."
Guzan's blunder handed Miami the opening goal in the 40th minute.
After easily grabbing a cross into the box, Guzan went to boot the ball away -- only to stumble and loose control with Miami's Federico Redondo running along beside him. Redondo sent the free ball to David Martínez, who casually flicked it over four United defenders into the unguarded goal while Guzan looked on helplessly.
The 40-year-old keeper claimed he was interfered with by Redondo, but the replay appeared to show Guzan tripping himself up.
In the 89th, United missed a prime chance to grab the lead when Saba Lobjanidze rocketed one off the crossbar. Bartosz Slisz collected the ricochet, but fired it over the net.
Silva made sure it didn't matter.
Miami was without Sergio Busquets, with Martino saying afterward that the midfielder suffered a knock in the first match with Atlanta and experienced the initial symptoms of pneumonia, forcing him to miss training this week.
"When you are missing a player like Busquets, any team feels it, obviously it does," Martino said.
Miami won the opening game of the series 2-1 at home.
Martino said he is confident his team can handle the pressure of a decisive Game 3.
"There is a lot of hierarchy in the team with many players who have gone through much more difficult situations than this, and we also have a way of playing that we have never changed," he said.
The winner of Game 3 will advance to the conference semifinals, facing the team that emerges from the Orlando-Charlotte series. Those teams are also tied 1-1.
Information from ESPN's Lizzy Becherano and The Associated Press contributed to this report.