Ben Bolger, the UAE captain, has been forced to retire because of concussion.
The flanker, who led Abu Dhabi Harlequins to an unprecedented five major titles last season, suffered a second head injury in the space of four weeks on Friday.
He made the decision to finish playing, age 28, due to fears over the repeated effects of multiple concussions in the 23 seasons he has been playing rugby.
“It is all I have ever known, to be involved in a rugby club,” Bolger said.
“It is a massive decision, but I think it is the right one. It is not like a bad hamstring. Concussion is something that could affect me later in life.
“More and more people are waking up to it, and pulling out of the sport because of it.
“They have been coming more and more often. I have had too many in my time, so it is time to call it a day.”
After ending a professional career in rugby league in the UK to move to Abu Dhabi to take up a job in finance, Bolger has enjoyed a sparkling career with Harlequins.
In the five seasons he played, for example, he reached five Dubai Rugby Sevens finals, winning the past three, and creating "memories I will take with me for the rest of my life" in the process.
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“Coming out here to play rugby, for me it was always going to be a social thing, to get to know people,” Bolger said.
“I was taken aback by how much people still wanted to be competitive, even though it is an amateur league over here.
“Even though people have careers, they want to dedicate a lot of their time to their squad. As you become involved and give your time, you want to be the best you can be.”
Bolger said the increased education in recent times about the potentially lasting effects of concussion led to him to decide against trying to play on.
“That is what I have done since I was 15 years old,” he said.
“I have had a couple of concussions every year since then. The recent education about concussion because of what has happened in the NFL has had an effect.”
Mike McFarlane, the Harlequins coach, said they were losing a “player who breathes our club culture”.
However, he is happy with the decision his captain made, for the good of his health.
“Rugby is not his income anymore, it is not his job,” McFarlane said.
“As a really good mate of mine, I said to him, ‘Your job is going really well, you have a wife, life is good – it only takes one more knock for it to be very serious.’ You never know.”
Harlequins lost 10 players from their all-conquering first XV before this season even started. Bolger’s absence is likely to be more keenly felt than any, however.
“He is an inspiring leader and a top-class player,” McFarlane said.
“We have been through some battles together, couldn’t have had a better season last year, and I’ve learnt a lot from him.
“As a good friend, it’s the right decision, and, like any player at the club, their health and safety is paramount.
“He will still be involved, imparting wisdom on the boys, and will continue to be an important part of the Quins make up.”