Roosters enforcer Dylan Napa may not play again until the 2014 Telstra Premiership Grand Final after being found guilty of a shoulder charge at the NRL judiciary on Tuesday night.

Napa pleaded not guilty to the hit on John Sutton in the 16th minute of last Friday's clash with the Rabbitohs but the judiciary panel upheld the charge.

The Roosters' legal representatives then challenged the grading of the offence and were ultimately successful in having it reduced from a Grade 2 to a Grade 1, thus reducing the length of his suspension from three weeks to two.

Napa's availability to play again this season is now dependent on the Roosters results in coming weeks, with a win on Saturday night ruling him out until the Grand Final, should the Roosters make it to the decider.

If they were to lose on Saturday night Napa would be available for the Preliminary Final provided the premiership favourites progressed past Week Two of the Finals Series.

It serves as a double blow to the defending premiers with Aidan Guerra electing to take the early guilty plea on a Dangerous Contact charge and accepting a one match suspension.

The Roosters said in a statement on the club's website that a decision on Napa's replacement on the bench would be made at a later date.

The judiciary panel will sit again on Wednesday night with Titans pair Beau Falloon and Tom Kingston challenging the grading of their Dangerous Throw charges stemming from the same tackle in their win over the Bulldogs last Sunday.