The Spaniard booked his place in the final of the London event on Sunday thanks to a straight-sets win over the Swiss in the semi-finals at The O2.
"The most satisfying thing always is the tournament more than the personal victories," Nadal told reporters.
"So for me it's more important to be in the final in the last tournament of the year than having the chance to win against Roger.
"To be able to win the final is much more important than any victory against any opponent."
Nadal will now face Novak Djokovic in the final on Monday.