The Russian outfit welcome Paulo Fonseca's men to the Petrovsky Stadium on Wednesday having won the reverse fixture in Portugal 1-0 last time out.
Spalletti wants his charges to concentrate on their own performance, although he also noted that Porto remain a good side despite the loss of players such as Hulk - who is now at Zenit.
"We will be in excellent condition. For us it makes no difference how the Portuguese play as we are thinking about how to win," the Italian said.
"I've seen all of Porto's recent games and I think they are a very strong team who continue to enjoy success every season despite the loss of some important players. It doesn't matter how they have played recently, the only thing that is important is what happens on the pitch."
Just a point separates the sides in Group G, with Zenit a place above their visitors.
Spalletti noted that both sides boast a similar level of quality and that the match will likely be decided by other factors.
"Skilful players can play a decisive role. I think that when playing against other teams at this level, both have a number of talented individuals and it is the tactical nuances that decide the outcome," he continued.
"The result will also be determined by the mentality and the team spirit shown.
"They will come to get the three points and we need the same thing. Let's wait and see who gets what they want. For a strong team there is no obstacle - not even rain or snow should stop us from playing our own game."
