Captain Alviro Petersen has described Glamorgan's defeat against Essex in the FL t20 as their worst performance of the campaign.
"We just played arguably one of the poorest t20 games of the season," he said.
"You have to play good cricket in all areas to win t20 cricket. We didn't have enough runs on the board and our fielding wasn't up to standard."
However Petersen admitted his side would not have been worthy of the win.
"It was good to bring it into the last over," added the South Africa opening batsman.
"It could have been different had we taken our catches [and] if a couple of things had gone our way.
"But at the end we weren't good enough and we don't deserve to get a victory."
Glamorgan will hope to bounce back from the Essex defeat when they host Sussex in Cardiff on Thursday.
And Petersen wants an improved performance against a side who are currently top of the South Group.
"It's a massive game," he said. "We've come unstuck here in two games at the Swalec Stadium, which we wanted to make our fortress.
"We want to get back to winning ways against Sussex. They're a tough team, they're top of our group and we really want to compete against the very best.
"I think it's a great opportunity on Thursday to do just that."