But the Italian Astana rider, 29, has no doubt he was ready to produce a "great race", even if Froome and Contador were in contention.
Defending champion Froome (Team Sky) crashed out on stage five and Contador (Tinkoff-Saxo) five stages later but Nibali's victory was rarely in doubt.
Nibali, who ended up winning by seven minutes 37 seconds, said his preparation held him in good stead.
"I think I would still have done a great race but for sure it would have been harder because they are both great climbers and great leaders," he said.
"But I prepared well for this race and it showed on the mountain stages. At every mountain finish I was there. I was feeling great.
"Froome and Contador are great champions and I hope I will be able to race against them next year."
Nibali said getting through the cobblestones stage on July 9 was the key to his general classification victory.
"The cobblestones stage [stage five] was the most important for the overall victory," he said.
"I was nervous about that day although I knew I could do something great. My sports director said 'go out and enjoy it' and I said 'what is there to enjoy? It's pouring with rain'.
"But I rode calmly. I think my mountain bike experience helped on that day as I felt in control of my bike."