Blues coach Pat Lam says that he is concerned about Benson Stanley's health and playing future after he suffered concussion playing against the Crusaders.

The former All Black centre's career is now hanging in the balance after this latest concussion which is his fifth major head knock in less than a year.

Lam said that it is possible that Stanley will have to go through a series of tests to assess how bad his most recent injury is.

"Bit concerned, another concussion, and he's had a few now" Lam told NewstalkZB.

"Well he hasn't had one this year, but obviously on the back of last year with Auckland when he had that last one."

"You know, there is concern but the medical team are monitoring that and go through the normal protocol, so he could be out for a while."

Last season Stanley took indefinite leave from playing rugby after neurological tests revealed limitations in memory capacity and reaction time.

Lam said that the Blues have not ruled Stanley out for the rest of the Super Rugby season but that they are preparing as if that is the case.

However with the profile of concussion symptoms peaking at an all time high, Stanley is likely to take some time time in considering his future.