Three years ago today, veteran goalkeeper Cassio went viral for displaying exceptional IQ during Corinthians' Brasileiro Série A clash against Atletico Mineiro.

Cassio, who joined Cruzeiro in 2024 after 12 years at Corinthians, has amassed 815 appearances across spells at Gremio, PSV Eindhoven, Sparta Rotterdam, Corinthians, and now at Cruzeiro.

The 39-year-old has celebrated several exceptional moments during his two decades in the sport, including his one appearance for Brazil in a friendly against Japan in November 2017, but few have been more memorable than when he showcased his genius in a viral clip.

Cassio once let a free-kick fly into his own net for a clever reason

A huge part of sport is knowing the game's rules inside out, and Cassio certainly displayed his knowledge of the game during Corinthians' showdown with Atletico Mineiro in November 2023.

When Mineiro were awarded an indirect free kick 74 minutes into the match, the Brazilian shocked almost everyone inside the stadium when he jumped out of the way of a cross and allowed the net to bulge.

While many accused him of match-fixing, the goalkeeper was actually showcasing his in-depth knowledge of the rules. According to the FA's Laws of the Game rulebook, if an indirect free kick is fired directly into an opponent's goal, then a goal kick is awarded.

But if the ball had touched Cassio before finding the net, the goal would have counted. Instead, the spoils were shared at one apiece, and the experienced shot stopper received his flowers for understanding the rules of the game more than anyone else.

Lesser-known football rules

Not being able to score directly from an indirect free kick is one of several rules that many forget about, demonstrated by the initial reaction to Cassio's 1000 IQ play against Mineiro.

Another lesser-known rule that is often forgotten is that players are still awarded a yellow card for taking their shirt off after scoring, even if VAR eventually rules it out.

Under IFAB Law 12, taking off your shirt or committing an excessive celebration is an independent bookable offense the moment it happens, regardless of whether the goal itself ultimately stands.

Arkadiusz Milik was once cruelly penalised for the rule during Juventus' dramatic Serie A clash against Salernitana in 2022. An overjoyed Milik thought he'd scored a dramatic 94th-minute winner for Juve and whipped his shirt off in celebration, completely forgetting he was already on a yellow card.

The referee promptly issued a second yellow and sent him off. Moments later, VAR reviewed the goal and disallowed it for an offside infringement by a teammate. While the goal was cancelled and the game ended 2-2, the Polish forward's red card remained completely valid, and he was suspended for the next game.

Others may not know that if a player passes a free-kick or throw-in back to the keeper and the ball ends up in the goal, it doesn’t count as an own goal. Instead, a corner is awarded to the opposing team.

This very rarely happens, but famously did during the Midlands derby between Birmingham City and Aston Villa in 2002.

Villa’s Olof Mellberg ended up throwing the ball into his own net, though if goalkeeper Peter Enckelman didn't touch the ball before it went into goal, it wouldn't have counted. Unfortunately, he was judged to have mishit it off his laces, making it one of the most iconic own goals in Premier League history.