Michael Duberry says Oxford have a team capable of giving Cardiff a tough match in their Carling Cup tie at Kassam Stadium.
Oxford were beaten 1-0 at Rotherham in their League Two opener, with Duberry missing a great chance to open the scoring early on.
But the 35-year-old is confident his side can bounce back from the disappointment and cause an upset in the season's first cup match on Wednesday night.
"It's a big game, big club and a good cup to go far in," Duberry told the club's official website.
"Judging on our pre-season every club that's come down to play us have sent a team out to win and we've done the same and we've won.
"We've taken some big scalps so if we take that attitude into the Cardiff game there's no reason why we haven't got a great chance of beating them."