Rounding off our review of the 2021 season, ATPTour.com looks back at the biggest Grand Slam upsets of the season, starting today with three of the top five upsets. We’ll review the top two tomorrow. 5) Roland Garros, First Round, Pablo Andujar d. Dominic Thiem 4-6, 5-7, 6-3, 6-4, 6-4A defeat