Kyrgios loses his cool

Nick Kyrgios faces the prospect of another season-ending ban after branding an official ‘‘a joke’’ before sensationally quitting his first-round match at the Shanghai Masters.

Tennis officials told AAP there was ‘‘an ongoing investigation’’ after Kyrgios stormed off the court after losing the first set 7-6 (7-5) in a tiebreaker to Steve Johnson, in apparent protest against the umpiring of Irishman Fergus Murphy.

Incredibly, Kyrgios’ dramatic walk-off comes after the volatile star was suspended from the ATP Tour for tanking at the very same tournament in China 12 months ago.

Kyrgios failed to front media in Shanghai before releasing a statement blaming illness and a sore shoulder for his conduct, which leaves his immediate playing future in doubt once again.

However, cameras caught the 22-year-old hot-head abusing the umpire and threatening to quit the match if replays proved officials’ line calls to be wrong.

‘‘He’s walking a fine line,’’ said a television commentator.

Kyrgios had received two code violations for unsportsmanlike conduct – the first for smashing a ball out of the stadium – and expressed his dismay at Murphy for copping a point penalty after swearing during the tiebreaker.

Kyrgios was in command of the breaker leading 4-2, only to erupt when he was delayed on serve.

Officials reportedly mistakenly allowed spectators to enter the arena when the two combatants changed ends and.

‘‘Poor officiating by you. You are a joke,’’ Kyrgios fumed.