Last year was supposed to be the last of active U.S. Open competition in the cozy old Grandstand that abuts Louis Armstrong Stadium on the Billie Jean King National Tennis Center grounds. The Grandstand was to have been used only for practice these next two weeks.

A new, larger Grandstand has gone into service on the opposite side of the tennis campus and, after this edition of the Open, both Armstrong and the Grandstand — show courts since the tennis center opened in 1978 — will be ripped down and replaced by a new Armstrong, with a roof.

But one of the refurbished field courts is not ready, so the old Grandstand is getting one more grand stand. And it began, with an exceptionally sparse crowd rattling around its 6,000 seats, with a low-visibility matchup between 32-year-old Belgian Steve Darcis, ranked 106th in the world and in the main draw as a qualifier, against 22-year-old Australian Jordan Thompson, ranked 91st.

Starting just after 11 a.m. Monday, they played for four hours and 11 minutes. Darcis won, 5-7, 3-6, 7-6 (5), 6-4, 7-5.

Bellis returns, wins in straight sets

Qualifier C.C. Bellis of Atherton, Calif., ranked 158th in the world, returned to the Open for the first time since making a big splash at Flushing Meadows as a 15-year-old in 2014. That year, Bellis knocked off Slovakia’s Dominika Cibulkova, who had been the Australian Open runner-up, in the first round.

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Monday, Bellis won in straight sets over Switzerland’s 65th-ranked Viktorija Golubic. Cibulkova, now ranked 13th (as she was then) and a 2016 Wimbledon quarterfinalist, Monday won her opening match over 83rd-ranked Magda Linette of Poland in straight sets.

Oh, brother

Germany’s Mischa Zverev, 29, older brother of 28th-ranked Alexander Zverev, who might be the Next Big Thing, needed four sets to defeat 25-year-old Frenchman Pierre-Hugues Herbert, ranked 114th.

U.S. has most participants

This year’s Open commenced with 53 nations represented in the combined men’s and women’s singles draws. The United States predictably had the most representatives among both the men (17) and women (22). France’s 13 men and Germany’s 10 women was the next largest contingents.

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Williams sisters up next

Both Williams sisters will be in action on the Open’s second day/night: No. 6 seed Venus against Ukraine’s Kateryna in Arthur Ashe Stadium’s third day match and No. 1 Serena against Russia’s Ekaterina Makarova in Ashe’s first night match.