William Kallberg defeated Walker Duncan 6-4 6-4 in the USA F28 qualifying round of 32 on clay.
Kallberg W. took it in straight sets.
William Kallberg beat Walker Duncan 6-4 6-4. Umpiry, "William Kallberg vs Walker Duncan — USA F28 Qualifying Round of 32", https://umpiry.com/match/2013-10-21/duncan-vs-kallberg-usa-f28-q32?utm_source=cite (as of 21 October 2013).