Waratahs captain Dave Dennis praised the side's character and ambition but admitted that execution let them down in their opening 25-17 Super Rugby loss to the Reds.

The Waratahs scored the first points of the match but let the Reds score two quick tries which forced the visitors to chase the game.

Trailing 17-3 at half time the Waratahs hit back and scored 14 unanswered points and draw level only to let the game slip at the death.

"We worked hard to get ourselves back in the game but you just can't give a team like the Reds that much possession," Dennis said after the game.

"It was positive that we put ourselves in the position to score tries but we just weren't finishing them off. It's our first game but we can't let that slip, it's disappointing."

Of his side's much improved second half performance, Dennis said, "As soon as we went back to how we wanted to play, we scored two good tries. "

"We held on to the ball and made some good gains.

"We've just got to know when to push that pass and when to hold on to it. "

"We created opportunities, we've just got to hold on to the ball better."

The Waratahs return to Sydney where they host the Rebels next Friday at Allianz Stadium.