It's the result of Machado dragging his left foot into Brewers first baseman Jesus Aguilar's leg while running out a ground ball in the bottom of the 10th inning in Game 4 of the National League Championship Series on Tuesday.
Brewers outfielder Christian Yelich called the incident a "dirty play by a dirty player" and aimed a couple choice expletives at Machado for good measure. Meanwhile, Milwaukee infielder Travis Shaw said he was sure the kick was intentional.
In any case, this certainly wasn't the first time Machado's rankled the feathers of an opposing team. Here's a selection of some others:
Machado's collision with Aguilar wasn't even the first time during this series that he's drawn the ire of the Brewers. During Milwaukee's Game 3 victory, Machado twice broke up plays at second base by sliding toward shortstop Orlando Arcia.
He got his hand up during the first slide and Arcia didn't attempt a throw. The second slide, in the fourth inning, was a bit different. Machado didn't make a play for the base, and he was found to have violated the rules when he grabbed Arcia's leg.
It's been a pretty controversial series for the 26-year-old.
As a member of the Baltimore Orioles, Machado went head to head with the rival Boston Red Sox on the regular, and tensions reached a boiling point in April 2017. While advancing on a ground ball, Machado slid through second base and his foot spiked the leg of infielder Dustin Pedroia.
It wasn't the first time Machado found himself in hot water against the Red Sox, either. In 2016, he slid hard into second base and narrowly missed upending shortstop Xander Bogaerts in the process.
It should be noted that the slide into Bogaerts wasn't deemed a violation of the rules. However, Machado had already developed a reputation for sliding hard into second base, as he'd done the same type of thing earlier in the season against the Chicago White Sox (which also wasn't deemed a rules violation).
Machado was on the receiving end of a 99-mph fastball from Kansas City Royals right-hander Yordano Ventura in June 2016. He immediately charged the mound and started throwing fists.
Afterward, the infielder said he didn't regret his involvement in the fight, as he assumed Ventura had plunked him intentionally.
"He hit me with a 99-mph fastball and 99 is no joke. You can ruin someone's career," Machado said.
Machado's toss was the culmination of a tension-filled series against the A's. It likely started when third baseman Josh Donaldson applied a hard tag to Machado's chest days earlier, which also resulted in both benches emptying.
As one of the best players in the game, Machado is primed to receive a massive contract when he hits free agency in the offseaon. It will be interesting if he winds up playing alongside a player he's clashed with, or in front of a fan base that's cursed his name.