British No.1 Jack Draper was forced to retire from his quarter-final match against France's Ugo Humbert at the Japan Open due to an apparent abdominal issue.

Despite receiving on-court treatment and attempting to continue, Draper eventually withdrew while trailing 7-5 2-1.

The 22-year-old had been playing his first ATP Tour tournament since reaching the semi-finals of the US Open earlier this month.

World No. 19 Humbert will now face Czech player Tomas Machac in the semi-finals.

The start of the match had been briefly delayed by rain, with both players leaving the court as the roof was closed. 

After a series of breaks in the opening games, Draper called for medical assistance but was unable to continue, eventually conceding the match.

Draper was also playing in the doubles event at the same tournament alongside Machac, who he would have played in the singles semis.

But the pair have been forced to grant a walkover to semi-final opponents Ariel Behar and Robert Galloway, who now progress straight to the final.