Chelsea defender Branislav Ivanovic admits the nerves are jangling in the Serbia camp ahead of their World Cup opener against Ghana on Sunday.[LNB] Ivanovic also acknowledged it was a major plus for his side that they will not have to face his Chelsea team-mate Michael Essien in the Group D showdown, a player he rates as one of the top midfielders on the planet.[LNB]Speaking about the mood amongst the Serbia players as they prepare to play their first World Cup as an independent nation, Ivanovic said: "It's the normal thing, we're feeling a little bit nervous before the start of the World Cup because for every player it's very important to play at the World Cup.[LNB]"We're feeling nervous but we're positive and I think we're ready."[LNB]When asked how important psychologically it is to start with a good performance and if he would settle for a draw in their opening game, the 26-year-old added: "I will be happy if we play like we did in qualification. The most important thing for everyone is that we are ready for the World Cup."[LNB]Serbia finished above 1998 world champions and 2006 runners-up France at the top of Group Seven in qualifying, during which time they collected 22 points and conceded just eight goals in 10 games.[LNB]The chances of Radomir Antic's side building on that fine showing with a victory over Ghana at Loftus Versfeld stadium on Sunday have been boosted by the absence of Essien from the Ghana squad.[LNB]Essien was ruled out of the tournament last month due to the knee and ankle injuries that saw him barely play any competitive football since December.[LNB]Ivanovic said of Essien: "Mike is a fantastic player, and it's very difficult for him because he has two big injuries and he cannot take a risk but for us it's good of course that he can't play. For me I think he's one of the best midfielders in the world."