By Paulo Prada

RIO DE JANEIRO (Reuters) - A year ago, Mireia Belmonte was injured and unsure whether she would even be able to compete at the Rio Olympics.

Now, after a come-from-behind victory in the 200 meters butterfly, the 25-year-old is the first female swimmer to win a gold medal for Spain and a contender for a fifth career medal if she qualifies on Thursday for Friday's 800 freestyle final.

"I didn't think I was going to recover and that it would be difficult to make the Olympics," Belmonte told reporters in describing her efforts to overcome two shoulder injuries last year. "But I made it and in the best possible way."

Admitting she was still nervous, the 25-year-old from Catalonia, a silver medalist four years ago, said she could not quite grasp her accomplishment upon exiting the pool after an enthusiastic crowd cheered her powerful finish.

"I couldn't believe it," she said. "I can't believe it now."

Australia's Madeline Groves, who began the race with a sizeable lead but whom Belmonte passed in the final lap of the race, took silver just 0.03 seconds behind.

"I knew that the second 100 meters were my forte," Belmonte said before recalling how difficult it was. "I suffered a lot in the last few meters."

Returning repeatedly to the pain and work that allowed her to heal and succeed at the Games, she said she sometimes still struggles to stay motivated. At times in her career, she has also been plagued by a sensitivity to chlorine.

"Some days it doesn't seem like it's worth it," she said.

But now, with one gold and the prospect of another medal, she is eagerly looking forward.

"It's what I dreamed about my whole life," she said.

(Additional reporting by Amy Tennery; Editing by Greg Stutchbury)