British No. 2 Daniel Evans was defeated by Japan's Yoshihito Nishioka 6-2, 7-6 (3) in one hour, 49 minutes in the first round of the Korea Open on Tuesday.
Evans, the No. 5 seed for the tournament, has lost all six of his previous meetings with Nishioka.
Elsewhere, American Jenson Brooksby downed Taiwan's Tung-Lin Wu 7-6(5), 3-6, 6-0 in two hours, 22 minutes to advance to the second round.
Wu will face South Korea's SoonWoo Kwon -- who defeated compatriot Yunseong Chung -- in the next round.
Lucky-loser Ryan Peniston lost in straight sets to Nicolas Jarry while American Mackenzie McDonald eased past Pedro Martinez.
Steve Johnson edged two closely-contested sets to defeat South Korean Ji Sung Nam in one hour, 34 minutes and Christopher O'Connell's retirement meant that Chun Hsin Tseng advanced.
Information from the Associated Press was used in this report.