A frustrated Walsh was penalised in the final minutes of the 18-12 defeat after allegedly firing an expletive at referee Chris Butler.
However, the circumstances are in dispute, with the Queensland State of Origin young gun denying his comments were directed at Butler.
"Yesterday while on the field I swore at another player. Whilst I don't promote this language to be directed at anybody I would never direct this type of language towards a referee," Walsh posted on Instagram on Monday.
His captain Adam Reynolds backed his claims.
"Show the full clip. Was talking to a player on the other team," Reynolds commented on a Fox League social media post that referred to the incident.
The Match Review Panel's move to call Walsh straight in could be due to the seriousness of the alleged offence, which included a number of swear words, or for further investigation.
The charge is Walsh's fourth this year, after he incurred two in Queensland's victory in Origin II, following a citing in round 11 for a shoulder charge.
Walsh said on Instagram he had "reached out to Chris Butler to apologise if he thought I was speaking to him".
"Whilst I am not proud of this ... I also want to let the public, and in particular young kids playing the game know that I would never swear at a referee and neither should anybody else," he said.
The Broncos will back Walsh's version of events at the judiciary.
The 20-year-old is competitive and passionate about his football but the club has been working with him since he was a teenager to deal with the emotions that surface on the field.
Reynolds has spoken with him previously about cooling his heels when things don't go his way.
Meanwhile, South Sydney's Jacob Host faces a two-match ban with an early guilty plea after being charged for an alleged shoulder charge on North Queensland's Tom Dearden.
Host was put on report in the 79th minute of the Rabbitohs' 31-6 defeat after racing out of the line to take out the young five-eighth. He will miss three games if found guilty.
His teammate Cameron Murray faces a fine for a careless high tackle, also on Dearden.
