Evans, 34, fell at the back of the court in the first game of the deciding third set, letting out a loud cry and immediately signalling he could not continue.
The world number 59 has endured a tough season and looked to be in tears as he sat on his chair.
Having not won on the main ATP Tour since March, Evans played superbly to win the first set 6-4, before Nakashima levelled by taking the second 6-3.
But the British number three’s hopes of earning a morale-boosting victory were dashed in the cruellest manner.
“I’m heartbroken at the minute. It’s tough,” said Evans, who will have a scan in the next 48 hours to determine the extent of the injury.
“If I miss the Olympics or Wimbledon, it would be a tough one to swallow, no doubt.”
On the court next door, 29-year-old Harris earned the best win of his career by beating Argentine world number 32 Tomas Martin Etcheverry.
Harris, who only earned his first win on the ATP Tour last year, recorded a 6-4 3-6 6-3 victory in his first-round match.
As a result, he will climb to a career-high ranking inside the top 150 next week.
