Arsenal youngster Emile Smith Rowe was taken off on a stretcher during the first half of Tuesday's Carabao Cup third round tie against Championship side Nottingham Forest.
The 19-year-old was involved in a sickening clash of heads with Forest captain Jack Robinson shortly before half-time, and had to be tended to on the pitch for several minutes by medical staff.
He was eventually replaced by Bukayo Saka.
Smith Rowe was said to be suffering from "a mild concussion" by commentators at the match, although at the time of writing there hasn't been a full diagnosis from Arsenal medical staff.
Smith Rowe was making his second appearance of the season after starting the 3-0 win over Eintracht Frankfurt in the Europa League group stage clash last week, after which he was praised by Gunners boss Unai Emery for his performance in a confident Gunners victory.
The young Englishman is back at the Emirates Stadium this season having joined German side RB Leipzig on loan for the latter half of 2018/19, during which he made three appearances for his temporary club.
Prior to that he played six games for the Gunners first-team last season, scoring goals against Qarabag and Vorskla in the Europa League and Blackpool in the Carabao Cup.
The Gunners led 1-0 at the time of Smith Rowe's departure thanks to a goal from summer signing Gabriel Martinelli, who later scored the final goal in a 5-0 win.
Arsenal boss Unai Emery opted to make 11 changes to his side following thr 3-2 win over Aston Villa on Sunday, with Smith Rowe and Martinelli among the players to come in.
Mesut Ozil captained the side, while Scottish full-back Kieran Tierney made his first appearance for the Gunners following his summer arrival from Celtic.
