San Francisco Frontiers - Another injury blow for Monfils as he retires in Miami

The 36-year-old left the court, wincing in pain with his match with compatriot Ugo Humbert at 3-3 in the first set.

At Indian Wells, Monfils lost to Jordan Thompson in straight sets in the first round, in what was his first tournament in seven months.

Last year Monfils had heel surgery after missing the French Open and the entire grass season.

His return from a three months absence, in Montreal, saw him suffer a foot injury and he subsequently announced the end to his season in October.

Monfils told AFP that while the injury was painful he would have to wait for scans before knowing more.

"We will have the exams and see what's happening," he said.

But after another blow after his long road back to competition, Monfils said he may have to consider his future despite his desire to carry on.

"I don't know, you know. I don't know. Of course, you have goals and you want to achieve some goals, but sometimes you have to have a step back and see," he said.

"And then, of course, if one day I cannot anymore, I cannot anymore. But I will do everything to keep playing," he said.

Monfils said it was purely the enjoyment of playing that kept him pushing to return to full fitness.

"The love of the sport, you know, the love of the sport. I love what I'm doing. I love my sport," he said.

"You know, I could have stopped a long time ago, but I still enjoy it. I'm still enjoying myself," he said.

Monfils was the second Frenchman to retire on Wednesday with Arthur Rinderknech quitting his tie with Japan's Taro Daniel in the first-set after receiving medical treatment.

Rinderknech, who was 4-1 down at the time he retired, was suffering from abdominal problems, according to a tournament spokesperson.

Umbert will face 29th seeded Serbian Miomir Kecmanovic in the second round.

J.Scott--SFF