Captain Michael Vaughan admitted England were under-par in all facets of their game as they slipped to a 108-run defeat to South Africa in Cape Town.
"We weren't quite on our game in all three departments and South Africa fully deserved their victory," he said.
England have played four matches in what Vaughan called a "hectic week".
But he added: "There's no excuses - we must come back on Wednesday and try and play a little bit better and put them under some pressure."
Kevin Pietersen, who hit a defiant 75, pointed the finger at England's bowling at the death, and the inability of team-mates to stay with him.
"They scored 60-odd in the last five overs and I don't think we got our yorkers quite as we discussed.
"And we didn't get any partnerships going, which you need chasing a big total," he said.
"We've got three games to go so we just have to keep the momentum going and we could still nip the series."