Zanetti made his comeback after seven months out with a torn Achilles tendon and could get his first start tomorrow.
Mazzarri said: "It's true Zanetti could start, but he might not have 90 minutes in his legs. If he were to start, I'd have to take that into account with regards to substitutions. I do have a doubt between Andrea Ranocchia and Rolando, but it's good to keep everyone on their toes.
"Nobody has the first team shirt stuck to their shoulders. I look at the team to get the best out of individuals and I live only for the results of the side."
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