Defending champ, 2013 winner fall in Tiburon openers

   Two Tiburon champions lost their opening matches in this year's Challenger, and a third nearly joined them.
   Wild card Brandon Nakashima, a University of Virginia sophomore from San Diego, ousted sixth seed and defending champion Michael Mmoh of Bradenton, Fla., 5-7, 6-3, 6-4 today in the second round at the Tiburon Peninsula Club. All 16 singles seeds received first-round byes.
   Mmoh, also the Tiburon runner-up in 2016, cracked the top 100 for the first time at No. 96 by winning last year's tournament for his second title in two weeks. But the 21-year-old son of former pro player Tony Mmoh will plummet 79 places to No. 287 on Monday. Michael Mmoh sat out for four months early this year because of injuries.
   Also today, Sekou Bangoura of Bradenton beat 12th seed and 2013 Tiburon champion Peter Polansky of Canada 6-1, 6-4. Polansky, 31, won last week's $54,160 Columbus (Ohio) Challenger on an indoor hard court.
   Bangoura also surprised fourth-seeded Dustin Brown, a German who's 2-0 against Rafael Nadal, in the first round at Tiburon in 2015 as a qualifier before losing to Mackenzie McDonald of nearby Piedmont in the second round.
   Seventh-seeded Darian King, the 2016 Tiburon champion from Barbados, topped another 21-year-old American, Ulises Blanch, 2-6, 7-6 (2), 7-5.
   Meanwhile, Ecuador's Roberto Quiroz, a Columbus semifinalist last week, dispatched second-seeded Denis Kudla, a 27-year-old American who lost a thriller in the 2015 Tiburon final, 6-3, 6-2 in 61 minutes.
   Top-seeded Tommy Paul of Greenville, N.C., beat wild card Brandon Holt, a USC senior and the son of International Tennis Hall of Famer Tracy Austin, 5-7, 6-3, 6-2. Paul also defeated Holt in the second round in Tiburon last year, 5-0, retired (shoulder).
   Here are the updated Tiburon singles and doubles draws and Thursday's schedule.