"Despite starting third, it was always clear keeping the Ferrari and Red Bulls behind was not realistic," he added.
"I lost two places right at the start, but then the pace was good and, especially towards the end, I was able to catch up quite a bit again. I kept the Mercedes behind with Nico leaving no room for me making any mistakes."
2012 Lewis Hamilton - McLaren
2011 Sebastian Vettel - Red Bull
2010 Fernando Alonso - Ferrari
2009 Rubens Barrichello - Brawn
2008 - Sebastian Vettel - Toro Rosso
Sauber team principal Monisha Kaltenborn added: "We could see in qualifying it wasn't looking bad, we were looking at maybe sixth or seventh but for Nico to drive like he did was fantastic.
"This results show we are moving in the right direction and that's what we all need."
The news in Monza was not so good for McLaren's Jenson Button, who finished in 10th place, one below his starting position.
"I had a bad start when my clutch slipped, and I dropped a few places," he said.
"That first stint was quite good fun, but, once I got stuck behind Daniel [Ricciardo], there was no way of getting past him."
Italian GP: Paul Di Resta crashes out on first Monza lap
"We didn't get the gear ratios quite right today. Consequently, as our fuel loads decreased, and our cornering speeds should have increased, we were hampered by our rev-limiters, and that made it easier for the cars behind to overtake us and harder for us to overtake the cars ahead of us."
Another man left disappointed was Scot Paul Di Resta whose race was over inside the first lap, as he rear-ended Romain Grosjean and was later reprimanded following an investigation by the stewards.
"It has been one of those weekends to forget, starting with the brake failure yesterday and the early retirement today, he said.
"I just got caught out going into the second chicane because the cars ahead of me got backed up - I guess they were reacting to the tussle going on ahead of them.
"I locked both fronts trying to stop the car and ended up hitting Grosjean. Unfortunately it was too late to take avoiding action. Now we need to look forward to Singapore and put this one behind us."
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