Reds captain James Horwill says his team lacked confidence in their 13-23 loss to the Stormers on Friday.

Horwill scored the only Reds try but was replaced late in the match after a shoulder injury to join a lengthy list of injured Reds players.

"We felt we created enough opportunities but we didn't convert," Horwill said.

"We didn't back ourselves to get over the line."

"We just have to be a lot more critical with what we do."

"They scored a lot of points from turnovers, so that was pretty disappointing."

The Stormers were captained by Duane Vermeulen in the absence of regular captain Jean de Villiers who was sent home earlier in the week.

Vermeulen said the Stormers were pleased with the victory after their suffered their first loss of the season last weekend when they played the Crusaders.

"We wanted to work on our attack a little bit more after last week's loss and we pulled it off," said Vermeulen.

"It was very humid out there, so we were very pleased to get away with the win."