New York Red Bulls star Kaku was the talking point of Major League Soccer and beyond after his 88th-minute meltdown saw him sent off after he smashed a football into the crowd, leaving a fan with a bloody nose.
Kaku, full name Alejandro Romero Gamarra, was clearly frustrated at seeing his side concede a late equalizer to Sporting Kansas City, and let those frustrations get the better of him.
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After a stray pass for him went straight out for a throw-in, a clearly-irate Kaku turned and hammered the ball from the touchline into the stands, hitting a fan in the face, knocking them off their seat.
The Argentinian playmaker was immediately sent off by referee Robert Sibiga, and he raised his hands in apology as he made his way off the field.
The fan reportedly had to receive medical treatment after sustaining a bloody nose from the incident.
After the final whistle blew, other members of the Red Bulls team went over to the fan to apologize for their teammate's meltdown.
And later that night, Kaku took to social media to post an apology for the incident.
"I want to take the time and apologize for my actions during tonight's match," he tweeted, alongside a photo of the Sporting Kansas City team lined up in front of their fans.
"As a competitor, I was frustrated with myself and took out my frustrations in a way that is not acceptable.
"I love this game and would never want to disrespect it."
He continued: "I apologize to the @SportingKC fans, my teammates, @MLS and to all @NewYorkRedBulls supporters."
The New York Red Bulls also issued a statement after the game, which read: "The New York Red Bulls organization does not condone the type of behavior displayed near the end of Sunday night's match in Kansas City. We hold everyone in our organization to a high standard of conduct.
"The matter will continue to be discussed internally and we will have no further comment at this time."