Mascherano, 40, is a former teammate of Miami star Lionel Messi. The two were teammates at FC Barcelona from 2010-18.
Miami had won the regular season campaign with a record points total but after losing twice in the best-of-three series, the MLS Cup favourites and their eight-times Ballon d'Or winner are out.
Portuguese winger Xande Silva blasted home a sensational winner for Atlanta in the fourth minute of stoppage time in front of 68,455 home fans at the Mercedes-Benz Stadium to level the best-of-three postseason series 1-1 and set up a winner-take-all game three in Miami next Saturday.
Miami started with all their big-name stars, including Lionel Messi, on the bench but the Argentine was introduced in the 61st minute to the delight of many in the Toronto crowd.
Messi had been subdued until the 45th minute when he put Inter ahead -- chesting down a long ball into the box and getting a lucky bounce off Crew defender Malte Amundsen before poking home.
Messi tied Saturday's match in the 67th minute when he lasered a shot from beyond the box that evaded diving Charlotte goalkeeper Kristijan Kahlina to make it 1-1.
Inter Miami's charge towards Major League Soccer's single-season points record suffered a setback on Saturday after a last-gasp injury-time equalizer from James Sands snatched a 1-1 draw for New York City FC against the Eastern Conference leaders.
The Argentinian superstar Messi came close to a game-clinching goal in the 83rd, but his angled effort was blocked by Atlanta goalkeeper Brad Guzan and Suarez's attempt to tap in the rebound was also denied.
The eight-times Ballon d'Or winner hadn't played since injuring his right ankle during the Copa America final on July 14, when he helped Argentina to victory over Colombia.
Miami, once again without Lionel Messi, who continues to be sidelined by an ankle injury, have already secured their place in the playoffs and remain in top place for the regular season 'Supporters' Shield'.
"There were specific drills that we devised that would allow him a certain level of participation," coach Tata Martino told the outlet. "But he still does not have medical clearance (to play)."
Luis Suarez struck twice as ten-man Inter Miami became the first team to book their place in this season's Major League Soccer playoffs after beating Cincinnati 2-0 at Chase Stadium on Saturday.
Messi, 37, has been away from the team since he suffered a high-ankle injury on July 14 playing for Argentina against Colombia in the Copa America final.
Diego Rossi's two second-half goals launched the reigning MLS champion Columbus Crew over defending champion Inter Miami 3-2 to reach the Leagues Cup quarter-finals on Tuesday.
Argentine star Lionel Messi was ruled out on Monday by Inter Miami coach Gerardo Martino for the defending champions' Leagues Cup knockout match on Tuesday at reigning MLS champion Columbus.
Messi suffered a right ankle ligament injury in last month's Copa America final, helping Argentina to victory over Colombia, but Martino said the 37-year-old Argentine striker is getting better.
Paraguay's Matias Rojas opened the scoring in the ninth minute and Uruguayan striker Luis Suarez added an insurance goal in the 72nd minute to deliver Inter Miami's triumph.
Lionel Messi will not play for Inter Miami as the defending Leagues Cup champions begin their repeat bid on Saturday (Sunday morning in Bangladesh time) at home against Puebla, Miami coach Gerardo Martino said Friday.
Lionel Messi will miss Inter Miami's next two Major League Soccer matches after injuring his right ankle in Argentina's Copa America final triumph, Miami coach Gerardo Martino said Tuesday.
