Gabriel Martinelli said he is "deeply sorry" for shoving Conor Bradley off the pitch and revealed he has apologised directly to the seriously injured Liverpool defender.
Martinelli threw the ball at Bradley and manhandled him as he lay on the turf in the closing stages of Thursday's 0-0 draw at the Emirates.
Bradley, 22, left the stadium on crutches and wearing a supportive brace on his left knee.
Martinelli was booked for the flashpoint, which provoked anger from Liverpool’s players.
Former Manchester United captain Roy Keane called Martinelli "a disgrace" on Sky Sports.
But in response to the backlash, Martinelli posted a story on his Instagram account, writing: "Conor and I have messaged and I have already apologised to him.
"I really didn’t understand he was seriously injured in the heat of the moment.
"I want to say I’m deeply sorry for reacting.
"Sending Conor all my best again for a quick recovery."
Prior to Martinelli's social media post, Arsenal manager Mikel Arteta defended his player.
Speaking in his post-match news conference, Arteta said: "Knowing Gabi, he's an incredible, lovely guy, and he probably didn’t realise what happened.
"I hope that Conor is well, I will have a word with him to understand that. Probably (Martinelli) didn’t recognise what happened."
Bradley struck the crossbar in the opening half of a cagey contest, but now looks set for a significant spell on the sidelines.
"I fear the worst for Conor Bradley," said Liverpool manager Arne Slot.
"I don’t know yet but he had to go off on a stretcher. We’ll have to wait on the scans to see if it’s that bad."
Of Martinelli’s response, Slot continued: "I don’t know Gabriel Martinelli but he comes across as a nice guy.
"The problem in general in football is that there’s so much time-wasting and players pretending to be injured, that you can be annoyed that you think a player is time-wasting.
"You cannot expect Martinelli to think so clearly in the 94th minute. I’m 100% sure that if he knew what the injury might be, he would never do that."
Liverpool captain Virgil van Dijk said was less forgiving and said of the incident: "Everyone was unhappy at that moment.
"It wasn't a couple of players, but everyone, and rightly so because Conor was on the pitch and to be pushing him off the pitch is not really a good sight.
"The long ball came, Conor is challenging for it, falls down on the pitch and obviously Martinelli pushes him off the pitch and our players reacted.
"We all came together. And we had no clue what really happened, but it doesn’t look great, and it doesn’t look great on Martinelli either."
Speaking on Sky Sports' coverage of the game, pundit Roy Keane called Martinelli's action "a disgrace," though Arteta appealed for understanding on behalf of his player.
Arsenal dominated the first half without much troubling Alisson in the Liverpool goal, though the visitors had the best chance of the opening period when Bradley hit the bar following a mix-up between David Raya and William Saliba.
Slot's team then had the better of things after the break but there never looked like being a winner.
"In the second half, we dominated the ball possession for almost the whole 45 minutes in their half," he said.
"The only thing that missed maybe from my side was again, for all the ball possession, all the moments around the box, you're hoping to create even more chances."
The result keeps Arsenal six points clear at the top of the Premier League after Manchester City and Aston Villa also drew on Wednesday.
Asked whether it had been a missed opportunity to pull clear, Arteta said: "Yes, every time you don't win. But then we would be 12, 15, 20 points ahead. I have to really praise the team and the players individually for what they've done in this Christmas period.
"The demands and the schedule, it's unbelievable. What they've done is remarkable. To come out of this period, with all the issues that we had, in the strong position we are, I think the boys deserve everyone's recognition."
