Britain's Andy Murray was forced to dig deep before beating rising Czech star Jiri Vesely in the third round of the BNP Paribas Open at Indian Wells on Monday.
The Wimbledon champion won 6-7 (2-7) 6-4 6-4 but only after clawing back from the brink of defeat against the 20-year-old Vesely.
Murray lost the opening set despite going up an early break but began to struggle on his own serve against the left-handed Vesely, ranked 77th in the world.
The Scotsman was broken six times in the match and trailed in both the second and third sets but fought back each time, reeling off four consecutive games to seal victory.
Murray will play either Canada's Milos Raonic or Colombia's Alejandro Falla in the next round as he bids to win one of the few North American hardcourt titles to have eluded him.
Switzerland's former world number one Roger Federer also advanced after a tough workout on Monday.
Federer, the four-time champion, was pushed all the way by Russia's Dmitry Tursunov but won two tiebreaks to triumph 7-6 (9-7) 7-6 (7-2).
China's Li Na, the top seed in the women's draw, had no problems booking her place in the fourth round, easily beating Karolina Pliskova of the Czech Republic 6-3 6-4.
Despite having her own service broken twice, Li was far too strong and streetwise for Pliskova, wrapping up win with an ace.
Li is looking to win her first Indian Wells title and continue her great start to the year after capturing the Australian Open.
Her next opponent is Canada's Aleksandra Wozniak, who defeated Russia's Anastasia Pavlyuchenkova 6-1 6-7(3-7) 6-0.