Zenit haven’t lost a point in the Champions League. They also are trying to move up in the Russian Premier League, winning against Ural last weekend. They are already in the play-offs so that’s why they can now relax. All the leaders of the team are fit.
Valencia lost to Gent in the last game of the Champions league. Besides that they don’t really play well in La Liga. The team is not fully fit right now. Particulary the conditions of the game vs Zenit will be unfamiliar to Valencia. It’s cold there already!
That’s why I can bet on Zenit to win the game in front of their passionate fans. But Valencia will score as they scored twice in the first match between them. Another reason for that is the fact that Zenit’s defence occasionally makes raw mistakes.