Three mates got another man drunk and drugged in an effort to rob him of $600.
However, the attackers, who king-hit their victim in a city park, found only $25 on him and his cellphone.
They failed to find the $600 he had hidden.
In the New Plymouth District Court on Thursday, Jason Richards, 36, pleaded guilty to aggravated robbery after being given a sentencing indication by Judge Allan Roberts hours earlier.
Two of the jointly charged defendants are yet to plead.
The judge told Richards he would jail him for 30 months.
Richards had 114 previous convictions.
Richards' lawyer, Jo Woodcock, asked for a pre-sentence report and time to look into the prospect of a restorative justice conference with his victim.
Sentencing was adjourned until May 15.
- Taranaki Daily News
Should the media report suicide?