Milos Raonic defended his title, defeating unseeded Denis Istomin in straight sets in the final.
Jesse Levine was the defending champion but was defeated in the First Round by Tennys Sandgren.
Michael Russell won the final 6–3, 6–2 against Bobby Reynolds.
Go Soeda successfully defended his title, defeating Mischa Zverev 7–5, 7–5 in the final.
Milos Raonic was the two-time defending champion and won the title for the third year in a row, defeating Tommy Haas in the final 6–4, 6–3.
Tim Smyczek was the defending champion, but lost to Cedrik-Marcel Stebe in the semifinals.
Denis Kudla defeated Stebe 6–3, 6–3 in the final to win the title.
Denis Kudla was the defending champion, but chose not to compete.
James Ward defeated James Duckworth in the final.
This was the first edition of the event.
Denis Kudla was the defending champion but chose not to compete.
Michael Russell defeated Peter Polansky in the singles final, 7–5, 2–6, 7–6(7–5).
Go Soeda was the two-time defending champion but chose not to compete.
Kei Nishikori was the defending champion and successfully defended his title, defeating Ivo Karlović in the final, 6–4, 7–6(7–0).
Alex Bogomolov Jr. was the defending champion, but decided not to compete.
Tennys Sandgren was the defending champion, however he lost in the first round to James Duckworth.
John Isner was the two-time defending champion, and he won the title for the third straight year, defeating Marcos Baghdatis in the final, 6–3, 6–3.
Thiemo de Bakker was the defending champion but chose not to defend his title.
Denis Shapovalov was the defending champion but chose not to defend his title.
Malek Jaziri was the defending champion but chose not to defend his title.
Lucas Pouille was the defending champion, but lost in the semifinals to Milos Raonic.
John Isner was the defending champion and successfully defended his title, defeating Ryan Harrison in a rematch of the 2017 final, 5–7, 6–3, 6–4.
Grigor Dimitrov was the defending champion, but lost to Novak Djokovic in the third round.
Roger Federer was the defending champion, but chose not to participate this year.
