Stan Wawrinka was relieved to avoid becoming the first defending champion to suffer a first-round exit at the French Open after twice coming from behind to beat Lukas Rosol on Monday.
Wawrinka beat Novak Djokovic to win his first title at Roland Garros last year, but the third seed was in danger of falling at the first hurdle on day two before prevailing 4-6 6-1 3-6 6-3 6-4.
The Swiss made 46 unforced errors and knows he can ill afford a repeat of his opening performance on Court Philippe Chatrier as he attempts to defend his title and win a third grand slam.
"It was a really tough match today. Conditions were really slow and heavy. It was typical first round [performance], for sure," Wawrinka said.
"I didn't play my best tennis, in general - a lot of mistakes. But he was playing really well, he was going for his shots and didn't miss much until he started to be a little bit tired in the fourth set and fifth.
"But before that I was always under pressure. The fact is that in the first round I'm looking a little bit for my game. The conditions were not easy to play freely with what I wanted to do."
He added: "It's a good thing to get through, but it's never, ever the best to start with five-set match and not play your best tennis. You always want to play good tennis and win matches in three sets.
"But today I'm really happy with the way I found a solution. It's a really good victory, good win for me, because it's the first match. He was playing really well. It wasn't easy for me to get into the match.
"I found a solution, so now I have a chance to keep improving for the rest of the tournament."