Arsenal forward Gabriel Martinelli apologized to injured Liverpool right back Conor Bradley after trying to push him off the pitch near the end of the 0-0 draw on Thursday.
Bradley fell awkwardly near the touchline in stoppage time and Martinelli clearly thought he was time-wasting, throwing the ball at him before manhandling him.
Liverpool's players reacted angrily and after the ensuing melee, Martinelli and Liverpool's Ibrahima Konate were booked.
Northern Ireland full back Bradley was eventually taken off the field on a stretcher in obvious distress.
"Conor and I have messaged and I've already apologized to him. I really didn't understand he was seriously injured in the heat of the moment," Martinelli posted on social media.
"I want to say I'm deeply sorry for reacting. Sending Conor all my best again for a quick recovery."
Martinelli's actions were branded "disgraceful" and Sky Sports pundit Gary Neville said the Arsenal forward had left him fuming.
"You cannot do that. That is so poor. I think an apology is needed," the former Manchester United defender said.
"Bradley is being stretchered off. I'm fuming with Martinelli, to be honest. Disgraceful. I'm surprised a Liverpool player hasn't gone over and whacked Martinelli there!"
Fellow pundit Roy Keane also criticized the Brazilian forward.
"I didn't like it. It's happened to me when I was badly injured and a player stood over me, and it's not good... I'm surprised the Liverpool players didn't react to Martinelli more. I think that behavior is an absolute disgrace. Not good scenes," Keane said.
Liverpool manager Arne Slot said he "feared the worst" for Bradley, although he was measured in his criticism of Martinelli.
"I am 100% sure that if he knew what the injury might be, he wouldn't do that," the Dutchman said. "But it doesn't look great if Bradley has the injury we think he has.
"You don't like to see a player being moved if he might have an injury."
Arsenal manager Mikel Arteta said Martinelli would never have tried to move Bradley if he thought he was injured.
"Probably he doesn't know because knowing Gabi, there is zero intention," the Spaniard said.
"I don't know what happened to Conor, but hopefully it's not bad, but obviously, there is no intention from Gabi to do anything bad to him."