The Argentine veteran made the telling contribution just after half-time with his first goal of the season, when he powered in a header that flew past Gianluca Pegolo.
That was enough to see Inter end a poor run of form that had seen them go winless in 2014, and Mazzarri was thankful to the experienced defender.
"Samuel? We've got world-class players up top and at the back, he's one of them, he's won everything. We needed a leader like him back there," the Inter coach told Sky Sport Italia.
"Obviously injuries and age have an effect, but the rest of the squad ought to watch and learn from the determination of Samuel."
Mazzarri chose to start with Diego Milito up front and he endured a frustrating game in search of his first goal since September.
The forward had two good chances saved by Pegolo in the first half, but Mazzarri put his inability to score down to bad luck.
He added: "Milito is such an important and intelligent player. He was unlucky with the chances, as one bounced right in front of him and another would've gone it were it not for a deflection, while Pegolo performed crucial saves.
"I'm sure he can only get better with more match fitness."
The victory was only Inter's second in their last 10 league games but it was still enough to move them into fifth in the table, and Mazzarri was pleased with the overall performance.
"We played well, it was tough and we know in Italy all opponents prepare tactically so they are balanced encounters," he said.
"We took a while to break the deadlock, which was rather familiar, but let's say we finally broke the spell.
"Both Hernanes and Fredy Guarin did well, though clearly they need to improve their fitness levels and can only get that with regular playing. You could tell Hernanes felt the tension of his debut."