Rafael Nadal is "almost impossible" to beat at the French Open and it is a "big ask" for Dominic Thiem to stop him winning a 12th title on Sunday, says ex-British number one Greg Rusedski.
Spanish second seed Nadal, 33, faces Austrian fourth seed Thiem at 14:00 BST in a repeat of last year's final.
"It is time for Thiem to step up in the biggest test in men's tennis on this surface," Rusedski told BBC Sport.
Thiem is seeking his first Grand Slam title, while Nadal is chasing his 18th.
The Spaniard can become the first player to win 12 singles titles at one Grand Slam.