YouTube star Jake Paul delivered a brutal knockout punch to former NBA guard Nate Robinson in their exhibition boxing fight on Saturday night. The vicious KO punch could have done serious damage to the 12-year NBA journeyman. After seeing the fight, several professional boxers were up in arms over these celebrity type matches. Most of their sentiments called for these kinds of fights to stop, saying that boxing isn't something you “play.”

Here are some reactions from pro boxers all over the world, via Phil Jay of World Boxing News:

“Can we stop with these BS YouTube fights? S— embarrassing and disrespectful to the sport. Boxing isn’t a sport to play with. These guys gonna get hurt,” said world champion Joseph Diaz Jr.

Ex-super-middleweight ruler Ishe Smith added: “F— (this YouTuber)! He proved nothing knocking Nate out. “Boxing is the only sport that would have this clown making more than 90 percent of fighters. Put his a– in with a real fighter.

Amanda Serrano, who has fought professionally both in boxing and MMA, also called for these celebrity bouts to stop, saying that people could get really hurt from it.

Former world champion Adrien Broner also took to Instagram to air his sentiments, saying that the sport isn't for everyone.

These professional fighters certainly did not hold back their feelings, especially after seeing Robinson take major damage in the fight. As you can see from their reactions above, they certainly didn't like “internet vloggers” like Jake Paul holding these kinds of exhibition fights just for the sake of it.

While they do throw punches for a living, these pro boxers still make sure to look out for the safety of everyone. Of course, boxing requires years of training. People like Nate Robinson, who only trained for a couple of months in preparation of these one-off gimmick bouts, could get serious damage if these fights aren't controlled.