Andy Murray stretches during his match with Robin Haase. (Kathy Willens/AP)

It was a day of somewhat close calls for two of the favorites in Flushing Meadows, New York, where the U.S. Open began today. After Venus Williams fought off Japan’s 43-year-old Kimiko Date-Krumm and a pesky bee to move on to Round 2, Andy Murray battled the Netherlands’ Robin Haase and pesky cramps to get to the second round.

The Scotland native, ranked eighth in the world, started off strong, capturing the first set 6-3, but he faltered later when cramps brought on by the sweltering heat almost did him in. Murray struggled to capture the second set 7-6 (8-6), completely lost his touch on the third when he lost 1-6, and fought hard against both the world No. 70 and his ailing body in the fourth to win 7-5 and clinch the match.

Murray looked visibly pained through much of the match, even choosing not to sit during breaks. But in the end, his perseverance paid off (although you wouldn’t know it from his post-game expressions, which still reflected his pain).

Murray will meet Germany’s Matthias Bachinger next in the second round.