Edinburgh's Scotland flanker John Hardie has been suspended from duty pending an internal investigation.
The New Zealand-born back-rower, 29, will not be considered for selection for either his club or for Scotland.
No further details were given, with a Scottish Rugby statement adding only that "we are unable to comment further given the nature of the investigation".
Hardie is therefore set to be omitted when Gregor Townsend names his squad for the autumn Tests on Monday.
It is the latest disciplinary issue to rock Edinburgh, with captain Magnus Bradbury already suspended pending the outcome of an internal hearing into how he suffered a head injury on a night out after Edinburgh's recent Pro14 win over Zebre.
It is understood the two incidents are not linked.
Open-side Hardie has won 16 caps since his debut in August 2015, which preceded him being drafted into Scotland's 2015 World Cup squad five weeks after arriving in the country from New Zealand.
A series of injuries, and the form of fellow Edinburgh flanker Hamish Watson, have limited Hardie to just three Scotland appearances this year, the last on the summer tour against Fiji.
Scotland head coach Townsend is already without two key players for the forthcoming Tests with Samoa (11 November), New Zealand (18 November) and Australia (25 November).
Injured Glasgow hooker Fraser Brown has joined captain Greig Laidlaw in being ruled out of all three internationals.