Darcy Graham will miss Scotland's Autumn Nations clash with South Africa on Sunday.
The winger scored four tries in the win over Fiji, but failed a head injury assessment (HIA) after being replaced in the second half.
Head coach Gregor Townsend confirmed Graham has failed his subsequent HIA tests and will miss the visit of the world champions to Scottish Gas Murrayfield.
He said: “Darcy unfortunately failed his HI2 and his HI3, so he'll be ruled out for this weekend."
Missing the chance to face the world champions is another blow for Graham, who has missed most of the last 12 months with injury.
The game against Fiji, in which Graham briefly tied Edinburgh team-mate Duhan van der Merwe for the Scotland try-scoring record, before the latter edged back ahead, was Graham's first cap since the Rugby World Cup defeat to Ireland 13 months ago.
Townsend outlined the road to recovery for the Hawick-born wing.
"It's a 12-day period, so he'll do nothing for the next three days, then he starts the graduated return to play, and if everything goes well and he's feeling good, he'll be available for Portugal.”
The Scotland head coach confirmed there was better news around another of Saturday's try scorers, however. Kyle Rowe limped off with a hamstring injury just before half-time, but he has not been ruled out of facing the Springboks.
He said: "Kyle Rowe is much better than expected.
"We had literally got his scan results back in the last hour, so we're not ruling him out for this week."
All the other 43 players who returned to the Scotland camp on Monday evening are fit and available for Sunday's game, with Blair Kinghorn coming through 80 minutes for Toulouse against Bayonne on Sunday night.
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