Golden State Warriors head coach Steve Kerr lamented the loss of Draymond Green in Tuesday's season-opening defeat to the Houston Rockets.

The Warriors started the defence of their NBA championship with a 122-121 reverse at Oracle Arena, despite having led by 17 points at one stage.

With Andre Iguodala (strained back) having missed the game, the Warriors were dealt a further blow when influential forward Green sat out the fourth quarter, in which the Rockets outscored their hosts 34-20, due to a left knee strain.

Green later told reporters that he was fine, but Kerr felt his absence proved costly.

"We deserved to lose" he said.

"We didn't have energy from most of our group.

"Draymond's injury changed everything for us.

"When we're lacking conditioning like we are right now, you have to have your high energy guys out there.

"As soon as he went out of the game, things went south for us. We just couldn't get any traction."