The Serb says they need to start killing off teams.
"We must play better and we need our players back from injury, but we believe we can win the league," he said.
"We have certainly shown this season we can play solid. We haven't lost.
"But this season is very strange. If you had told me five weeks ago that Chelsea would be in the position they are now, I wouldn't have believed it.
"Everyone thought they were the strongest team and that they would win the title. But then they didn't win for six games.
"And look how many points we have lost this season. If someone had told me this would happen, I would have said we could not win the league. But here we are top and still unbeaten."
He added: "If we had won just half of the away games we have drawn we would have been out of reach by now.
"But the other teams can say that too. They will feel they should be in a better position too.
"We just have to keep going and hope we can change it."