Britain's Andy Murray says he needs to remain focused as he prepares to take on Jo-Wilfried Tsonga in the men's quarter-finals at Wimbledon.
Second seed Murray has yet to drop a set at this year's tournament and the 2013 champion is the highest-seeded player remaining in the men's draw.
But the 29-year-old described Frenchman Tsonga as "one of the best grass-court players in the world".
"If he plays well, I'm not on my game, I can lose that match," said Murray.
Murray, competing in his ninth consecutive Wimbledon quarter-final, has beaten Tsonga in 12 of their 14 encounters - twice at Wimbledon.