All Black remains hospitalised

All Black Ben Smith's immediate playing future remains uncertain, with the Highlanders fullback still hospitalised in Sydney.

It is becoming more unlikely that Smith will be available for the Highlanders when they take on the Crusaders in a decisive Super Rugby Round 19 outing in Christchurch on Saturday.

The All Blacks fullback was hospitalised with an infection, following the Highlanders' loss to the Waratahs on Sunday and will now spend a third day in the Sydney hospital.

The infection is thought to have come from a superficial graze on Smith's leg.

It was hoped he would be discharged on Tuesday, but team doctor Greg Macleod says it's since been decided he needs to stay in hospital to continue treatment.

"Team doctor Greg Macleod, in conjunction with Sydney doctors, have decided to keep Smith in hospital overnight to continue treatment," the Highlanders said in a statement on Tuesday.

"Smith is responding well to treatment and is due for discharge tomorrow [Wednesday] morning where he is booked on a flight back to Dunedin first thing."

The Highlanders are placed fourth on the Super Rugby table with one round to go, but may need to beat the Crusaders in Christchurch on Saturday to ensure a place in the play-offs.

The Highlanders statement said a decision on whether or not Smith will play on Saturday is still to be made.