Andy Murray faces Croat Ivo Karlovic in the French Open third round on Friday after surviving five-set scares in his first two matches in Paris.
Second seed Murray has spent seven hours and 14 minutes on court against Radek Stepanek and Mathias Bourgue.
Davis Cup captain Leon Smith says Murray's good form before Roland Garros may be behind his initial struggles.
"If it doesn't quite go that way in the early rounds here, there's a bit of frustration," Smith said.
Murray's meeting with big-serving veteran Karlovic is the second match on Court Suzanne Lenglen on Friday at approximately 11:00 BST.