WASHINGTON — Stephen Strasburg isn't sure whether he will pitch again this season.

The Washington Nationals star left Wednesday's start in the third inning. Tests determined he has a strained flexor mass in his right elbow and the injury is not related to his ligament, which needed Tommy John surgery five years ago.

"I can't make that claim," Strasburg said about a 2016 return. "There's still pretty much a month left in the season. I'm just trying to get back healthy. Hopefully, we're still playing baseball."

Strasburg received his first platelet rich plasma injection Friday, a procedure in which his blood was drawn, platelets separated in a centrifuge and activated platelets injected back into the injured area to assist healing.

"I think the biggest thing is just seeing how it feels four, five days from now," Strasburg said, "then start progressing with a little bit more treatment and strengthening up the forearm and getting into some sort of throwing program."

Strasburg started the season 13-0 with a 2.51 ERA. The 28-year-old allowed 19 earned runs in 11 2/3 innings in three outings before going on the disabled, then lasted just three innings in his return.

"Unfortunately this has happened to me so many times that it's just like, I can just sit here and let it eat at me, which I've done in the past and it doesn't make it any better, so it's the cards that I've been dealt," he said. "I'm just trying to stay positive and learn from it and work even harder."

In Wednesday's start against Philadelphia, Strasburg felt a pinch in the back of his elbow that wouldn't go away.

"It was a little alarming to me," he said. "Even when I went out there for the third, it felt more like the seventh or eighth inning, which was kind of odd. I just tried to get it out and then felt something on a pitch and it didn't really go away. It just kind of stayed there. That's when I knew it probably wouldn't be a good idea to try to throw through it."

Still, there was relief when tests determined his ulnar collateral ligament was not damaged.

"It was about as good of news as you can get," he said. "So, I'm just trying to take it one day at a time now and do everything I can to get out there, not only as fast as possible but feeling right at the same time."