Lionel Messi and Inter Miami remain in MLS Cup despite last-minute Atlanta winner due to unique MLS rule

Lionel Messi and Inter Miami are still in the MLS Cup despite losing the second leg of their last 16 play-off fixture to Atlanta United.

Inter Miami won the first leg 1-0 last week, with a second leg taking place on Saturday night to give both teams another opportunity.

It was a rare off-night for Messi in terms of the goals and assists board, with Atlanta securing a dramatic 2-1 victory through former West Ham forward Xande Silva's injury-time winner.

But while, in other leagues, the game would either go to extra time and penalties after two legs, or be settled by away goals, the MLS does things differently in its play-off system.

Inter Miami and Atlanta United will now face off for a third time in the last 16 as part of a series to determine who goes through to the quarter-finals.

But the third game is only triggered if the two teams win a game each, with a best-of-three series played instead of simply just three matches.

And with both teams winning one match so far, they will have to do it all again next Saturday.

In fact, even in the case of a draw last night, a third match would still be played as Atlanta would still be able to match Inter Miami's record of one win, thus triggering extra time or penalties.

Inter Miami will be at home for the final leg, as they won the Supporters' Shield for the best regular season record.

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A similar system is used across American sport, with Major League Baseball (MLB) going up to a best-of-seven series in their postseason semi-final, while the World Series final is also a best-of-seven play-off.

And in the NASCAR Sprint Cup Series, the top 16 drivers are split from the rest of the field - in terms of the championship - and compete for the Sprint Cup in the final 10 races of the season, with four drivers being eliminated from each of the three three-race rounds before the final.

So while most fans of American sport will be familiar with those concept, those watching the MLS Playoffs for the first time this season were shocked at finding it out.

Taking to Twitter, one fan wrote: "Nah just discovered after two legs they have a third leg in MLS."

Another wrote: "Tf is a third leg in football."

A third said: "They play two legs then play a third because it was level???"

A fourth stated: "Three game series what a joke."