Former Australia test batsman Ed Cowan has been ruled out of the rest of NSW's Shield clash against WA in Christchurch and will be monitored closely by medical staff after copping a nasty knock to the head.

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Cowan becomes one of the first players to be treated under Cricket Australia's strict concussion guidelines which have been strengthened in response to the tragic death of Phillip Hughes.

The left-handed opener suffered a hit to the front of his helmet during his second innings and was assessed on the spot by NSW and Australian doctor John Orchard - the man on the scene on that fateful day at the SCG when Hughes was struck.


Cowan retired hurt after appearing rattled by the fast bouncer he copped from rookie Australian paceman Joel Paris.

"Advice from the doctor is that Cowan's health is in a reasonable state but as per the Cricket Australia concussion guidelines, he will be observed for the next 24 hours as a precautionary measure and not take further part in the match," said a NSW statement.

Test offspinner Nathan Lyon later described the incident as "nasty".

"It was pretty nasty. The medical staff will look after him and survey him overnight and hopefully he's all good ..." he said.

NSW batsmen Kurtis Patterson (5no) and nightwatchman Lyon (0no) took the offer of bad light in the next over with NSW on 1-11, still trailing the Warriors by 78 runs.