The Australian former world number one and 2002 champion was beaten 7-5 6-4 6-7 (7-9) 4-6 6-3 by Polish 15th seed Jerzy Janowicz in their second-round clash at the All England Club.
Asked if he had waved goodbye to the grass courts at Wimbledon for the last time, the 33-year-old Hewitt was uncertain.
"I don't know," he said.
"You never know. I'm one injury away from hanging up the bats at any time. I still enjoy doing the hard work and having moments like this, playing five-setters against the best guys in the world.
"After the last surgery I didn't think I'd be able to compete against the guys again, so I've been grateful to come back.
"The body felt fine out there which is obviously positive, but it's frustrating to walk off the court feeling like I could have bounced back for another five-setter tomorrow (if I had won).
"You don't get the opportunity."
Janowicz, who faces Spanish veteran and 23rd seed Tommy Robredo in the third round, praised Hewitt.
The 23-year-old said Hewitt's ranking (48) and age meant nothing.
"It's a really good win for me," Janowicz said.
"Lleyton Hewitt is a really dangerous player. Doesn't matter how old he is or what his ranking is now. He's an extremely good player, especially on grass.
"I hope I will not play against him any more."