Tottenham midfielder Dele Alli was struck on the head by a bottle during Spurs' 2-0 League Cup quarter-final win over Arsenal at the Emirates Stadium on Thursday (NZ time).
Alli was hit on the side of the head in the 73rd minute by a plastic bottle thrown from the stands.
The England international responded by holding up two fingers in the air to indicate Tottenham's 2-0 lead match.
Arsenal is analysing CCTV in a bid to identify who threw the bottle at Alli.
The win comes 17 days afar after Tottenham lost 4-2 to the same team in their Premier League clash and was also their first away victory over the Gunners in eight years.
South Korean star Son Heung-min scored Tottenham's first goal in the 20th minute, while Alli added a second in the 59th minute.
Tottenham are looking to win their first silverware under manager Mauricio Pochettino and their first since 2008, when they lifted the League Cup by beating Chelsea in the final.
In the day's other match, Chelsea beat Bournemouth 1-0 to reach the final four.
Tottenham will play Chelsea in the Carabao Cup semi-final, with Manchester City hosting League One side Burton Albion in the other tie.