Tsonga, the No. 2-seed, won more than two-thirds of the points on serve in a 6-7 (3-7), 6-2, 6-2 decision over sixth-seeded Edouard Roger-Vasselin. Tsonga didn't drop his serve -- saving the only two break points he faced.
He was unable to convert any of his third break chances in the first set but had a pair of break in each the second and third sets.
No. 1-seeded Richard Gasquet defeated fifth-seeded Ivan Dodig 7-5, 6-3 by saving five of the six break points he saw. Gasquet finished with three breaks on the day.
Gasquet will take a 2-0 career series edge over Gulbis into the semifinals while Tsonga and Struff will be meeting for the first time.