'Not taking chances': Blues react to another Beauden Barrett head knock

New concussion fears are hitting All Black Beauden Barrett's career with the Blues still unsure of his status after he left the field against the Highlanders.

Barrett was making his return to the Blues starters on Saturday night after battling concussion issues resulting from a head knock in November's Irish test.

The situation was so bad that the World Cup winner feared the concussion effects had prematurely ended his career.

The Blues say they decided to remove Barrett from Saturday's Super Rugby game in Dunedin after he took a big head blow which left him on the ground and requiring medical attention.

Blues coach Leon Macdonald says the brilliant playmaker had a "good fat lip and a bleeding nose" after his attempted tackle on charging Highlanders back Fetuli Paea went wrong.

MacDonald said it was a "no brainer" to immediately take Barrett out of the game.

"He's got good contact to the face, that's why he's got a bleeding nose and his lip," he said.

Beauden Barrett of the Blues lays on the ground after taking a knock to the head during the round six Super Rugby Pacific match. Photo / Getty Images.

"We're never going to take any chances with Beauden. We want to look after his health and make sure he's well, and it was an automatic decision really.

"Hopefully it's nothing too much more than that, but we'll have to track him and see how he turns up."

Barrett, who was replaced by Stephen Perofeta, had scored a try late in the first half to help set up the Blues 32-25 win.

MacDonald said the Highlanders' physical start to the second half had led to Barrett's injury.

"Brutal carries…bodies on the line stuff. Their cleanouts were ferocious in the second half, and he was on the end of one," MacDonald said.

Barrett suffered migraines during the offseason and often felt "sluggish".

"I thought it might be the end of my career…you assume the worst," he said last month.

"I wanted to not worry my loved ones but, deep down, I didn't feel well."