Slovenian NT and its coach Kek have been heavily criticized lately. Slovenia has been playing poorly since that win against Russia in Maribor 2 years ago (1st half against USA was an exception, but they bottled it in the 2nd and should have lost anyway) and critics are becoming louder and louder. Could be an extra motivation for the team and especially for players who are criticized the most (captain Koren, Novaković, Kirm, Jokić). The team has nothing to lose now and they'll be playing without pressure. Could be the last NT game for some players and coach (it's not sure whether he'll stay or not or whether he'll be sacked - this game could influence our FA's final decision). They'll surely want to proove themselves and show to the public that they aren't that bad, regain confidence. If they'll lose again, media will criticize them even more.
Personally, the way the team is playing right now, I don't see them having much chance against Serbia, BUT the team prooved in the WC 2010 qualifications that they CAN beat such teams when giving their best and when they're really motivated (their home form on that stadium in Maribor -where the match against Serbia will be played- was terrific, they won all home games except against Czech republic). It also has to be noted that this team kept 0-0 score against Italy up until very late in the game back in september.
As for Balkan rivalry, there is no real rivalry between Slovenia in Serbia. There is a rivalry between Slovenia and Croatia, but not with Serbia. Slovenian ultras will boycott the game because of a recent rift with Slovenian FA. Btw, a lot of Slovenian players have Serbian ancestry, like for example Novaković, Radosavljević, Dedić, Jokić ...
P.S.: So far, all our matches against Serbia were draws..