Houston Rockers center Dwight Howard has admitted to being left frustrated with his team's effort in recent losses.

Along with guard James Harden, Houston have one of the most effective offensive threats in the NBA but have struggled in recent games.

"[Expletive] effort out there on defence and on offence. It's gotta be important for guys to come out and play the same way every night," Howard told reporters.

The Rockets have suffered two straight losses, shooting just 35.2% from the field in the defeat to the Phoenix Suns on Wednesday night.