Vienna - Andy Murray defeated France's Gilles Simon for the 16th time on Thursday to reach the Vienna ATP quarter-finals and keep alive his bid to snatch Novak Djokovic's world No 1 ranking.
The Olympic and Wimbledon champion eventually triumphed 4-6, 6-2, 6-2 after two hours and 40 minutes in a match, which saw Murray commit an uncharacteristic 58 unforced errors.
Simon was almost as sloppy, hitting just three fewer.
Murray, the 2014 champion in Vienna, goes on to face John Isner on Friday for a place in the semi-finals.
If he wins the Vienna title and Paris crown next week, Murray could unseat Djokovic as world number one as long as the Serb star loses before the final in the French capital.
After dropping the first set on a frustratingly slow court, a weary-looking Murray had to save six break points in the second game of the second set to stay in contention and two more in the fourth.
But it was all one way traffic after those blips with the world No 2 sweeping four games in succession to level the match.
Simon, who had won just two of his 17 matches against Murray before Thursday, required a lengthy medical timeout before the final set to treat a blister on his right foot.
Despite hanging on for 2-2, Murray repeated the punishment he dished out in the second set to take the match.
Unseeded Serb Viktor Troicki earlier defeated third seeded Dominic Thiem of Austria 6-2, 7-5 a result, which qualified Gael Monfils into the eight-man field at the season-ending ATP World Tour Finals in London.
Results from the ATP Vienna Open on Wednesday (x denotes seeding):
Andy Murray (GBR x1) bt Gilles Simon (FRA) 4-6, 6-2, 6-2
Viktor Troicki (SRB) Dominic Thiem (AUT x3) 6-2, 7-5
Jo-Wilfried Tsonga (FRA x6) bt Philipp Kohlschreiber (GER) 7-6 (8/6) 6-2
Albert Ramos-Vinolas (ESP) bt Jurgen Melzer (AUT) 3-6, 6-4, 6-0