Frederick was going back with the flight of the ball when Webster cannoned into him during the first quarter of the Dockers' 9.18 (72) to 8.7 (55) win at Marvel Stadium on Saturday night.
Webster served a seven-match ban this year for a brutal late hit on North Melbourne's Jy Simpkin but was making a spoiling attempt when he crashed into Frederick.
The 153-game defender came from the opposite direction and effected the spoil in the contest.
The incident was scrutinised by the AFL match review officer, who determined on Sunday that Webster had no case to answer.
"Jimmy had eyes for the ball and was going for the ball," Saints coach Lyon told reporters after the match.
"It's a 'come forward to defend' game. Look, I've got confidence in the process and the system."
Frederick was flattened when he chased a Caleb Serong pass in the centre square and hit his head on the ground when he landed.
Michael Frederick has been subbed out early (concussion) after an early collision with Jimmy Webster.— Walyalup Football Club (@freodockers) Tom Emmett will come into the game.⚓� 2 👼 12#AFLSaintsFreo #KalyakoorlWalyalup pic.twitter.com/WJDuBsRCT4May 18, 2024
Nat Fyfe and other Dockers immediately ran to their teammate, who stayed down as St Kilda went forward and kicked the first goal of the game through Mitch Owens.
Medical staff brought out a stretcher after the goal but Frederick was able to get up and jog off the ground unassisted.
The 24-year-old speedster failed a concussion test in the change room and was substituted out for Tom Emmett before quarter time.
"He was good at halftime and he's good after the game," Fremantle coach Justin Longmuir said of Frederick.
"It was clearly a big collision ... so we'll monitor him and see how he goes.
"I'd have to have a look at it - I haven't really trawled back through the vision - but it felt like it was a footy act when I saw it."
In their commentary of the match, AFL games record holder Brent Harvey and Hawthorn legend Jason Dunstall both agreed Webster was contesting the ball.
"I don't think there is much more Jimmy Webster could have done," Dunstall said on Fox Footy.
"I also think the players recognise that. There was no remonstrating with Webster.
"When Freo players came in they didn't remonstrate because they know it was a fair contest."
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