The Metropolitan Police have released an image of a man they suspect of throwing a bottle at Dele Alli during Tottenham's 2-0 win over Arsenal at the Emirates Stadium in the Carabao Cup in December.
The Spurs midfielder was struck on the side of the head in the 73rd minute of the quarter-final clash by the plastic bottle thrown from the crowd.
The Met say they have been working with Arsenal to identify the suspect, but no arrests have been made and they are now appealing to the public for information.
PC Jonathan Fryar, who is leading the investigation, said: "This was a disrespectful act which showed complete disregard for both the players and the fans wishing to enjoy a peaceful match.
"The incident is being taken seriously and we have been working closely with Arsenal Football Club to thoroughly investigate."
Alli, who scored Spurs' second goal in the victory, responded to the incident by making a gesture to the crowd to indicate the 2-0 scoreline, before being led away by captain Harry Kane.
The 22-year-old then told Sky Sports after the game the incident made his goal "sweeter" and tweeted a picture of him gesturing to the crowd, along with a 'crying with laughter' emoji.