Westbrook had to limp off following the collision with Philadelphia's Furkan Korkmaz
Washington Wizards point guard Russell Westbrook had to be restrained by security after a fan poured popcorn over him during his side's 120-95 defeat at the Philadelphia 76ers.
The incident happened as Westbrook left the court with an injured ankle.
"I wouldn't come up to me on the street and throw popcorn on my head, because you know what happens," said Westbrook.
Atlanta Hawks guard Trae Young was also spat on in their play-off at the New York Knicks' Madison Square Garden.
The New York Knicks have now indefinitely banned the fan responsible for an incident which came against the backdrop of their first NBA play-off win in eight years.
The 101-92 win levelled their Eastern Conference tie at 1-1.
"We investigated the matter and determined that this patron, who is not a season ticket holder, did indeed spit on Trae Young, and for that reason, he is now banned from The Garden indefinitely," the Knicks said.
"This was completely unacceptable and will not be tolerated in our venue. We have turned the information over to the appropriate authorities."
Meanwhile, the 76ers have also taken action against the fan involved in the Westbrook incident.
They said the person involved would have his season ticket membership revoked and would be banned from all events at the Wells Fargo Centre indefinitely.
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"In these arenas, you have got to start protecting the players. We'll see what the NBA does," Westbrook said following the game.
The defeat meant the 76ers took a 2-0 lead against the Wizards in their Eastern Conference play-off.
The popcorn was thrown over Westbrook from above the players' tunnel as he went off with 10 minutes left of the fourth quarter and the fan was later ejected.
"This was classless, unacceptable behaviour, and we're not going to tolerate it at Wells Fargo Center," said Philadelphia's president of business operations Valerie Camillo.
"We're proud to have the most passionate fans in the country… but this type of behaviour has no place in our arena."
Elsewhere, the Utah Jazz moved to 1-1 in their Western Conference play-off with the Memphis Grizzlies after a 141-129 victory.
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