After weeks of fine tuning on clay-court venues at locations such as Monte Carlo, Rome, Barcelona, and Madrid, competitors began play at the crown jewel of the clay season on Sunday. However, mother nature made most of the news at Roland Garros as rain interrupted matches throughout the session. Only a handful were completed, ensuring a full schedule of matches on Monday, but not before another delay.

However, the rain would subside, and when play finally resumed on the grounds, defending champion Stan Wawrinka was quick to be tested. The unpredictable Lukas Rosol, whose results suggest that he often raises his level against the top players, pushed the No. 3 seed before Wawrinka gained control to earn a 4-6, 6-1, 3-6, 6-3, 6-4 win.

The Czech found success early with big-strike tennis and gained an advantage as a result. But after surviving an early assault, Wawrinka found his footing and had success measuring Rosol’s game. Yet that was short-lived as the Swiss fell within one set from elimination. It was at that point that Wawrinka gained control for good and finally won the back-and-forth match.

Wawrinka came to Paris fresh off of his title in Geneva and admitted he struggled with the damp and cool conditions, “It was a really tough match; the conditions were slow and heavy,” he said. The match was one of many delayed due to the conditions on Monday.

Jack Sock was a victim of a rain delay on Sunday and concluded an interrupted match on Monday, defeating veteran Robin Haase, 6-3, 7-5, 3-6, 6-7, 6-2. Sock appeared to be cruising to a straight-sets win when Haase fought back to even the match. The American found it difficult obtaining good traction as the rain fell during the first day of play.

However, he efficiently closed out the Netherlands native as play resumed. Sock controlled the tempo with his big serve and forehand and found enough success against his opponent’s serve to break twice and close out the match. The 23-year-old ventured to the net more frequently than normal, finding good success there.

The American was not a fan favorite of the local Parisians, who booed as he left the court. Reportedly, some fans did not appreciate a comment made toward Haase. Nonetheless, Sock was happy with his game, “Playing on the dirt is always a fun time for me,” he said. “I feel very comfortable on it.”

In the women’s draw, it was business as usual for most top seeds, but fourth-seeded Garbine Muguruza was forced to rally to advance past Anna Karolina Schmiedlova, 3-6, 6-3, 6-3. The Spaniard overcame a slow start and 53 unforced errors but remained true to her aggressive style and was finally rewarded in the final two sets.

The 22-year-old acknowledged that it was not her best effort but was happy to advance, “I'm just happy that I went through the first round,” she said. “Sometimes you don't play your best tennis, but you find a way to win, which is very important.”

One seeded player who was not so fortunate was Roberta Vinci. The No. 7 seed gave little resistance as she fell to Kateryna Bondarenko 6-1, 6-3.

Five Americans advanced to the second round as Sloane Stephens, CoCo Vandeweghe, Shelby Rogers, and Bjorn Fratangelo joined Sock with a successful opening effort.