West Coast midfielder Andrew Gaff says he feels sick after breaking Andrew Brayshaw's jaw with an unprovoked punch in the Eagles' 58-point win over Fremantle.
Gaff could be rubbed out for the rest of the AFL season after unleashing the blow in the third quarter of Sunday's 21.16 (142) to 13.6 (84) win.
The punch came as Brayshaw merely blocked Gaff's run about 25m off the ball.
Brayshaw dropped to the turf and lay there for an extended period, with blood pouring out of his mouth.
The 18-year-old kept his mouthguard in, fearing some of his teeth had been knocked loose, and was taken to hospital.
Fremantle confirmed Brayshaw's jaw was broken and four teeth were displaced, with the first-year midfielder booked for surgery on Sunday night.
The incident will go straight to the AFL tribunal and could attract a ban of between four and eight weeks.
Melbourne's Tom Bugg copped a six-match suspension for striking Sydney's Callum Mills in similar fashion last year.
But Mills wasn't seriously hurt, in contrast with what happened to Brayshaw.
"I just want to apologise to Andy," a remorseful Gaff told Fox Sports.
"I feel sick. I did the wrong thing and it doesn't indicate my character.
"My only thought is how Andy is and what will happen (to me) will happen."
Fremantle coach Ross Lyon said he was distressed by the incident and referred to Barry Hall's seven-week ban for a punch on Brent Staker in 2008 as a precedent for what the tribunal might hand down.
"Andrew Brayshaw was king-hit 100m off the ball," Lyon said.
"I've got an 18-year-old kid that I saw in a real mess when I came down to the rooms and his mum in tears as I was walking in. It's not very palatable.
"He was pretty distraught. I gave him a hug. I wouldn't like to see my son like that.
"My senior players certainly wanted retribution and I had to stay out on the ground longer at three-quarter time to settle a couple down."
West Coast coach Adam Simpson said the incident was out of character for Gaff.
"One thing I know is that Andrew's character and who he is as a person and a player can't be questioned," Simpson said.
"As much as it is going to look as though it was intentional, I'm not really sure it was."
Gaff appeared to be crying after on the bench late in the third quarter, with Simpson coming down to comfort him.
The midfielder returned to the field in the final term and continued to be targeted by Dockers players, and was eventually picked off by a fierce Michael Johnson bump.
Johnson, who retires at season's end, could be suspended over the incident.
Eagles goalsneak Liam Ryan could also be in strife for a high bump on Lachie Neale.
Gaff was able to play out the match and was mobbed by teammates after kicking a final-quarter goal in front of 57,375 fans.
Eagles midfielder Elliot Yeo won the Glendinning-Allan Medal as best afield for his 26-disposal, two-goal effort.
Second-placed West Coast (14-5) are six points clear of third-placed GWS and eight points clear of five other sides.