Ravichandran Ashwin's decision to mankad Jos Buttler, and the subsequent debates over the laws of cricket and the spirit of the game, have divided opinions of experts and fans alike. Cricket isn't the only sport where the line between the laws and the spirit of the game occasionally gets blurred. Here are a few other incidents that have caused fiery debates.

Kyrgios and Chang go underarm, and SABR

Interestingly, within a few hours of the Aswhin-Buttler incident, world tennis' bad boy Nick Kyrgios pulled out his drop-shot underarm serve to good effect in a straight-sets win against Serbia's Dusan Lajovic in Miami. It's a tactic the Australian is known for, and has even drawn the ire of players like Rafael Nadal for the unusual nature of it.

Underarm serves are not new in tennis, though, as a teenaged Michael Chang used them to brutal effect during his round of 16 match at the French Open 30 years ago against the world's top singles player Ivan Lendl. It was a tactic used more out of desperation than invention -- the 17-year-old Chang had begun cramping when two sets down against Lendl when he first tried it.

Perhaps Lendl could have used the SABR (Sneak Attack By Roger), which has become Roger Federer's calling card. It divides opinion, but as a cursory look on any of the YouTube playlists dedicated to it will prove that it can be very effective.

Messi's penalty, Ramos' yellow and dark arts in the penalty area

We know it feels like this happened just yesterday, but Lionel Messi passed the ball from the penalty spot to allow his Barcelona teammate Luis Suarez complete his hat trick against Celta Vigo more than three years ago. It wasn't the first time that this had happened in football, but it is definitely an unusual occurrence, especially if you think about how goalkeepers set themselves up to save penalties, looking for visual cues by following the penalty-taker's feet movements.

Speaking of goalkeepers, it is common for them to be hemmed in from all sides during opposition set-piece routines, including the unusual long throws that Rory Delap has brought into vogue in international football. One player who tends to do this often is Sergio Ramos, Spain and Real Madrid's combative centre-back who pulls no punches within his own penalty box or that of his opponent.

Ramos is known for stretching the rule book on a fairly regular basis, and that came back to bite him as recently as last month. Just one yellow card away from suspension in the Champions League knockout stages against Ajax, he got himself booked in the latter stages of the first leg with Madrid in cruise control, hoping to sit out the return fixture and then be reinstated for the following stage. UEFA would catch on to this and hand him an additional game ban, though Ajax turning the tie around and winning meant the ban wouldn't hurt the three-time champions in their title defence.

Schumi, oh Schumi!

In 2004, Rubens Barrichello had to make way for his Ferrari teammate Michael Schumacher when in sight of the finish line at the Austrian Grand Prix, under team orders to allow the German to consolidate his lead on the championship table. The margin of victory, 0.1 second, underscores how frustrating it might have been for Barrichello to make way, as he was on his way to his first chequered flag in 22 months, and just the second win of his career.

Schumacher, one of Formula One's all-time greats, also picked up his first driver's championship in 1994 in controversial circumstances. With a point separating himself and British driver Damon Hill going into the year's final race in Australia, he brushed the wall during the 35th lap with Hill just behind him and in a good position to overtake him. Schumacher appeared to turn in aggressively and made contact with Hill's car, which led to both drivers forced to retire, giving the German the championship by that one point!

Eye to eye

If you thought chess is just about two, stone-faced guys staring at the board, here's a bizarre instance from the past for you. The 1978 World Championship between 47-year-old Viktor Korchnoi and Anatoly Karpov, 20 years younger to him, was everything you'd not expect to happen at a chess game. Ahead of the start of the match, Korchnoi demanded that his opponent's chair be x-rayed to check for prohibited devices. To combat Karpov, who'd earned a notoriety of staring at opponents, Korchnoi turned up at the first game wearing mirrored sunglasses. Karpov complained to the arbiter that whenever Korchnoi raised his head, the lights on the stage were reflected into his eyes and was giving him a headache while Korchnoi alleged that his opponent's chair swiveling was a deliberate act to distract him.

The arbiters declared the glasses 'non disturbing' and Korchnoi continued to wear them for few more games. During Game 2, a waiter delivered blueberry yoghurt to Karpov in a tray which Korchnoi's team protested against, raising cheating allegations of it being a possible coded message. That wasn't all. Karpov claimed that a member of Korchoi's coaching team in the audience was trying to catch his eye in an attempt to hypnotize him and responded by employing his own hypnotist to stare at his opponent. A chess fan can't be faulted for not recollecting who eventually won the match.