Former champion Watson let his lead slip in round three on Saturday as inexperienced Spieth moved alongside his compatriot on five under par.
It’s going to be tough for everybody, not just guys that have never won one
The 35-year-old won the Masters in 2012, but Watson still expects to feel nerves as the pair start one shot clear of Jonas Blixt and Matt Kuchar.
“We are all going to be nervous,” said Watson.
“We all know what it means to our career, for our status to move forward in the game. It’s going to be tough for everybody, not just guys that have never won one.”
20-year-old Spieth is yet to win a Major and the Dallas youngster is under added pressure as he attempts to take Tiger Woods’s crown as the youngster recipient of a green jacket.
And as a former winner, Waston admitted he could console himself with his 2012 triumph in Augusta if his challenge should fade on the final day.
“If I play bad, I still have a Green Jacket, so that’s the positive I have to go for,” added Watson.
Watson also believes he and Spieth have an advantage as the pair tee off in the final group, like 19 of the last 23 Masters winners.
“That’s where everybody wants to be on Sunday,” Watson continued. “You know the roars, you know the history of the game. It’s a lot better making that putt to win when you’re in the last group than having to wait.”
MORE: The latest football news
MORE: The latest tennis news