He also told Sunderland's official website of the team's frustration at not being able to penetrate opposition defences.
He said: "They (Palace) played really defensively, so it was quite difficult, and it got a bit scrappy. I thought we could have pushed on a bit more for a goal, but it didn't come.
"But we need to work more on breaking teams down. Other teams have seen that we scored four goals at Sheffield, so maybe they're being more defensive against us."