Harlequins director of rugby Conor O'Shea has admitted that Mike Brown's recent high-profile head injury has left him feeling concerned.

The 29-year-old has not played since the final round of Six Nations fixtures on March 21, and is no closer to making a return to action due to ongoing issues following the heavy blow.

Brown himself insisted earlier this week that he has no intention of rushing back, while O'Shea has now revealed that the indefinite timescale is a big worry.

"It's a concern because I don't like someone coming in with something you can't diagnose," the Daily Mail quotes him as saying. "Sometimes a physio will sit you down and say, 'It's six to 12 weeks out'.

"Here it could be tomorrow or it could be whenever - we don't have a timescale. There's no doubt that a decade or even a year ago Browny would be back out on the pitch. You want to see the gladiatorial side of things - the big hits that we've all grown up with.

"It was once a badge of honour that you got up and got on with it. But at least we're now aware. Is it a concern for the game that we're seeing collisions of the nature that we are? Yes, it has to be."

Harlequins are also currently without Wales international George North, who is himself suffering from concussion problems, while Joe Marler and Chris Robshaw have featured in just eight of their side's last 18 games.