Glasgow Warriors second-row Leone Nakarawa's appeal against a three-week suspension has been rejected.
The Fijian had been cited and banned for a head-butt during Warriors' victory over the Ospreys last month but claimed there had been errors in the disciplinary process.
A Pro12 appeal committee dismissed these allegations.
Accounting for two "down" weeks where there are no Pro12 fixtures, he may return to play from Monday 30 March.
Nakarawa's original ban stood from 25 February, following the decision of a disciplinary committee in Dublin.
The lock has since missed Glasgow's 22-10 defeat in Munster and Friday's 26-5 win over bottom-placed Zebre ., and will be unavailable for the club's crucial trip to Leinster on 27 March as they look to retain their position at the top of the domestic table.
He was ordered to pay the costs of convening the hearing.
Nakarawa, the Pro12's top off-loader during 2013-14, has made 13 league appearances for the Warriors this season, scoring a try against Munster, and played a part in all six of their European Champions Cup fixtures.
In his absence, and those of Jonny Gray and Tim Swinson, both of whom are involved in Scotland's Six Nations campaign, head coach Gregor Townsend has relied chiefly on club captain Al Kellock and back-row James Eddie to fill the void in the engine room.
Flanker Rob Harley, also a mainstay of Vern Cotter's international squad, played second-row at age-grade level and was originally named to start alongside Kellock against the Italians before a late injury to Adam Ashe resulted in him reverting to the back-row.
Glasgow took Edinburgh pair Fraser McKenzie and Alex Toolis on loan as cover, although the former has since returned to the capital.