Former Tottenham midfielder Ryan Mason has criticised Wales' handling of Daniel James' head knock with the winger playing on despite laying motionless on the pitch.
The Manchester United star was involved in a collision with Croatia's Domagoj Vida during Wales' 1-1 draw at Cardiff City Stadium on Sunday.
Players and the referee immediately asked for medical staff to attend the incident as James lay on the field with his eyes closed.
The 21-year-old was allowed to continue playing after leaving the field for treatment, in a decision which angered Mason.
Daniel James was just knocked out unconscious! Yet 3 minutes later he has been allowed back onto the pitch 🤷♂️— Ryan Mason (@RyanMason) October 13, 2019
"Daniel James went down and stayed down with a bit of acting," said Wales manager Ryan Giggs.— Optus Sport (@OptusSport) October 14, 2019
"I didn’t get knocked out," James said.
Here's the incident 👇 #EURO2020 #OptusSport pic.twitter.com/ihxZ74KHOb
After being forced to retire in 2018 after suffering a sickening concussion while playing for Hull City, the 28-year-old was incredulous at the call by the Welsh medical staff.
"Daniel James was just knocked out unconscious! Yet three minutes later he has been allowed back onto the pitch," Mason posted on his Twitter account.
Following the match James denied he suffered concussion, saying he was 'fine' and that he 'didn't get knocked out'.
And his national team boss Ryan Giggs playfully suggested the flying attacker was making the most of the injury and said there was no negative effects from the incident.
"Dan James went down and stayed down. A bit of acting really," Giggs said.
"The medical staff went over. He was compos mentis. We did tests at half-time and he passed them. He's fine."
Mason's career was cut short in February last year after suffering a fractured skull in a collision with Gary Cahill at Stamford Bridge in January 2017.
Daniel James got knocked out cold and is still playing. That can not be good for the brain. #WALCRO— Isaac Nowroozi (@isaacnowroozi) October 13, 2019
Unbelievable that Daniel James is allowed to carry on after getting knocked out on the pitch. Barbaric. #WALCRO— brett (@brettwit) October 13, 2019
Daniel James has just been knocked out and is allowed straight back on. Absolute disgrace.#WALCRO— Mark Wilson (@Willo79) October 13, 2019
The then-25-year-old clashed heads with Cahill during a corner and was given oxygen as he received treatment on the field for 10 minutes.
He was then rushed to the neurosurgery unit of a nearby hospital for emergency treatment.
Mason returned to training with Hull in May 2017 but was eventually told "the risks involved had given him no option but to retire".
A 2017 study on deceased footballers from the NFL found 99 per cent of studied brains showed signs of Chronic Traumatic Encephalopathy (CTE) - which is a neurodegenerative brain disease found in subjects who are exposed to repeated head knocks.