A member of staff at a bar in Uplands, Swansea, was left with serious injuries after he was attacked.
The man suffered a fractured cheek and eye socket while trying to remove someone from the Optimist Bar and Kitchen.
Police are now hoping to speak to the man pictured in connection with the incident.
They have asked the public to come forward with information, including people who saw anything on the night - the evening after Wales won the Grand Slam.
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A South Wales Police spokeswoman said: "Police in Swansea are investigating an assault at an Uplands bar, which left a man with serious facial injuries.
"Officers were called to The Optimist, Uplands Crescent, at approximately 8.45pm on Saturday, March 16.
"The victim, a member of staff who was punched to the face after ejecting someone from the premises, required surgery for a fractured cheek and eye socket."
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She added: "Enquiries are ongoing and officers are keen to speak to this man in connection with the incident."
Anyone who witnessed the assault, or has any information which could help with the investigation, is asked to contact 101, quoting occurrence 1900094491.
