Yuki had won the first set 6-2 and was leading the second 1-0 when the Australian qualifier conceded the match after 42minutes due to shin pain in both the legs. (Agencies)
The Indian next faces Kiwi Michael Venus, who defeated Australia's Dane Propoggia 6-3 6-3 in his first round match.
Earlier, Yuki had lost in the doubles first round with American partner Mitchell Krueger. They lost 4-6 4-6 to local pair of Maverick Banes and Gavin Van Peperzeel.
Meanwhile, in the Eckental Challenger tournament in Germany, top seeded Indian pair of Divij Sharan and Purav Raja made a shock first round exit.
The Indians lost a hard-fought first round match 7-5 5-7 3-10 to local wild cards Robin Kern and Maximillan Marterer in one hour and 24 minutes.
In the Charlottesville event in the USA, both Somdev Devvarman and Saketh Myneni will open their campaigns on Wednesday.
Second seed Somdev is up against Samuel Groth of Australia while Myneni faces top seed and world number 84 American Tim Smyczek in his first round match.
Somdev will also compete in the doubles event with compatriot Sanam Singh. They will take on American wild cards Mitchell Frank and Mac Styslinger.
Yuki had won the first set 6-2 and was leading the second 1-0 when the Australian qualifier conceded the match after 42minutes due to shin pain in both the legs.