Batsman Kusal Perera left the field in the second test against Australia on Sunday after he was hit on the helmet, the second Sri Lankan player in two days to leave with a head injury.
Perera was to undergo a mandatory concussion test after he was unable to continue batting at Canberra's Manuka Oval in the first session of the third day.
At lunch Sunday, Sri Lanka was 215-7 chasing Australia 534-5 declared, trailing by 319 runs. Wicketkeeper Niroshan Dickwella was out lbw for 25 on the last bowl before lunch, and with Perera unsure of returning, could be eight wickets down.
Fast bowler Mitchell Starc has taken 3-54 for Australia.
Perera ducked into a ball from Australian fast bowler Jhye Richardson and received treatment on the field, with play stopping for several minutes. He tried to continue and add to his 29 but the play was stopped again shortly after as Perera left the field, which ended a promising 37-run partnership with Dhananjaya de Silva.
Perera was replaced by Dimuth Karunaratne, who had retired hurt on day two after being hit in the neck by a bouncer. Opener Karunaratne was cleared to return to the crease, less than 24 hours after being felled by a Pat Cummins delivery.
Australia vs Sri Lanka, 2nd Test: Dimuth Karunaratne taken to hospital after being hit on the head by a bouncer
Australia vs Sri Lanka, 2nd Test Day 2: Injury to Dimuth Karunaratne headlines disappointing day for visitors
The play was stopped for almost 15 minutes on Saturday as Karunaratne was treated on the field before he was put on a stretcher and taken from the field to Canberra Hospital by ambulance.
He was released on Saturday night and given the all-clear before Sri Lankan officials confirmed he could return to the crease.
Australia beat Sri Lanka by an innings and 40 runs in the first test at Brisbane.