Zhuhai, China: Nick Kyrgios fears he could face several weeks out after struggling with what he said was a "clicking" shoulder in a limp first-round exit at the Zhuhai Championships on Wednesday.
The 24-year-old Australian, who has been accused of tanking matches in the past, served underarm on one occasion and led the veteran Italian Andreas Seppi 4-1 in the first set.
But the unpredictable firebrand went down 7-6 (7/5), 6-1 in southern China after his game spectacularly fell apart.
Kyrgios, who has had numerous run-ins with tennis authorities down the years, said that he was "struggling a lot" — but he still played doubles soon after.
"I was battling with a bit of a shoulder/collar bone injury," said the 27th-ranked Kyrgios, a colourful but controversial figure.
"At this rate I'm not thinking about playing until my shoulder's — or I don't even know what it is — but until my front of my shoulder feels better and I can serve," he added, saying his right shoulder had been "clicking".
"I mean the reason I lost today was because I couldn't serve.
"If I could serve, it would have been a pretty routine win for me, to be honest."
Asked if he could sit out the next few weeks or even the rest of the season, Kyrgios replied: "For sure, I mean at this rate I wouldn't be surprised.
"I wasn't able to even serve at a reasonable pace.
"I'm probably not going to bother playing until I can get it right again," he added.
Kyrgios elicited a few giggles from a sparse crowd in Zhuhai with an underarm serve in the first set.
Coasting 3-1 and 40-0 up, Kyrgios served weakly into the net, before surging into a 4-1 lead.
But the Australian faded alarmingly from there and his previously dominant serve collapsed.
Kyrgios, who appears to revel as the "bad boy" of men's tennis, repeatedly felt his shoulder and his game disintegrated as lost the first-set tie break.
The second set was a non-contest as Seppi, 35, ranked 74th in the world, strolled into round two in 65 minutes.
Kyrgios said that he still hopes to play for Australia in the Davis Cup in November.
"So until now and then I've got a lot of time, I can rest, recover, get my shoulder right," he said.
Kyrgios has long divided tennis fans.
He is an undoubted talent but has a long list of misdemeanours including rowing with umpires and spectators, and throwing an on-court chair.
The Australian says he deploys underarm serves for tactical reasons, but Spanish player Rafael Nadal accused him of "lacking respect".