Amercian Ryan Harrison, the youngest player in the Top 250, made the quarterfinals at the Hall of Fame Tennis Championships earlier this year. (AP)
SI.com's daily menu of must-see happenings at the U.S. Open (all times Eastern).
• Ana Ivanovic vs. No. 21 Zheng Jie (Arthur Ashe Stadium, 11 a.m.): Shortly after the 2008 French Open championship and Ivanovic's dramatic ascent to the No. 1 ranking, it was Zheng who sparked the Serb's lengthy downslide with a third-round upset in that year's Wimbledon. Then ranked No. 133, Zheng became the third-lowest ranked player to defeat a No. 1. In the two years since, Ivanovic has tumbled down the charts, only recently showing improvement during hard-court season. Meanwhile, Zheng reached her second Grand Slam semifinal at the Australian Open earlier this year and showed tenacity in Monday's first-round victory over a game Timea Bacsinszky. Should be a cracker to kick off Day 3 on Ashe.
• Ryan Harrison vs. No. 15 Ivan Ljubicic (Court 11, 11 a.m.): Could the 18-year-old Harrison, one of the rising stars of American tennis, be ready for his close-up? Already the youngest player in the Top 250, the Louisiana native reached the quarterfinals at Newport this year before reaching the U.S. Open main draw by way of the qualifying tournament. Ljubicic hasn't done much in 2010 since a shock victory at Indian Wells -- highlighted by victories over Novak Djokovic, Rafael Nadal and Andy Roddick -- but the 31-year-old Croat's experience is a well-matched test of Harrison's development.
• No. 17 Gael Monfils vs. Igor Andreev (Grandstand, fourth match): The organizers stacked today''s bill on the Grandstand with crowd-pleasers and slotted Monfils as the headliner. The elastic Frenchman is tailor-made for the intimate stage and should feed off the audience's energy. But after Monday's taxing five-setter -- and more temperatures in the high-90s expected -- Monfils could be ripe for the upset.Others to watch: