In challenging Juventus for the Serie A title Mazzarri hopes the Azzurri will at least return to Champions League football next season but he is impatiently bidding to reach the later stages of this year's competition in order to meet the likes of Ajax, Chelsea and Lyon.
He told reporters: "We need to make the step up in quality that will get us through this round and pit us against teams from the Champions League.
"The club strengthened in January with a clear view to helping us move forward in two competitions, so I will always pick the strongest team available so we can progress both in Europe and in the league."
One such reinforcement was Portuguese defender Rolando, who arrived at the San Paolo on loan from Porto having won the Europa League under Andre Villas-Boas in 2011.
The 27-year-old said: "It's difficult to draw comparisons between Napoli and the Porto side with whom I won the Europa League, but we're at that team's level.
"I had no doubts when I chose Napoli because I knew it was a team that could fight both in the league and in Europe."
Czech club Plzen are unbeaten in their last four European games but defender Vaclav Prochazka remains wary of the competition's top scorer, Edinson Cavani, who has seven goals to his name and should line up for Napoli at San Paolo on Thursday night (6pm GMT).
He told fcviktoria.cz: "Cavani has excellent balance, decides matches and has scored a lot of goals this year.
"All the biggest clubs are interested in him so he is definitely an exceptional player, as is Marek Hamsik who I know from the international scene.
"I remember playing Fiorentina once. There was no whirlwind attack at the beginning, they decided to wait, but when they hit us they finished us off.
"It will be the same with Napoli and they have the advantage of Cavani, Hamsik et al.
"We will need to be 100 per cent focused at every stage of the game, even when they're not looking dangerous."