After the Dutchman was injured in the first half he took his anger out on the dressing room wall and is understood to have broken two fingers.
Janmaat went off after an awkward fall after a defence-splitting pass from Sadio Mane in the first half which eventually led to Graziano Pelle scoring the game’s second goal. He has suffered a groin injury and is being assessed but the damage to his hand will not rule him out of the Swansea City clash.
It is believed that Janmaat later admitted his actions had been stupid, but it is also understood there were some strong words from Newcastle players to each other after the appalling first half display.
Janmaat is now being assessed for both injuries picked up on and off the field.