Anthony Rendon is active for the first time all season. (Greg Fiume/Getty Images)

For the first time in 2015, Anthony Rendon is back on the Nationals’ active roster, reinstated Thursday after battling a sprained MCL in his left knee and a strained oblique.

The Nationals optioned Wilmer Difo to Class AA Harrisburg to make room for Rendon, who is expected to play second base. Rendon won the National League Silver Slugger at third base last season.

Rendon’s reinstatement ends what amounted to a months-long purgatory for one of baseball’s most promising young talents, one that began when Rendon dived for a ball in a spring training game on March 9. He slammed his left knee against the unforgiving Space Coast Stadium dirt, spraining the medialcollateral ligament in that knee. The Nationals initially expected him back after a few days of rest. Rendon said he think everyone was surprised by how long trouble lingered.

“There was a little frustration, but everything happens for a reason,” Rendon said. “I’ve been put in this position and I just have to go forward from here. “

After spending April resting and healing in Viera, Rendon headed back to the majors, stopping first for a late April rehab assignment. While there, he felt the twinge in his side that was later found to be the strained oblique. He was relegated to rest again

“I think just gradually I felt (the oblique), then it got worse and worse, and then I thought I could play through it,” Rendon said. “It kind of makes sense of not hindering myself for like three or four months out, so kind of playing through the lighter part of the year. We have to be smart about it.”

Last week, Rendon began a rehab assignment with Harrisburg, and this time it stuck. He played five games, three at second and two as the designated hitter. He played two games Wednesday, and had a hit in each. He had 18 at-bats in those games, far fewer than he would in a normal spring training workload, but as Nationals Manager Matt Williams said, if Rendon hits a double, the Nationals want him to hit it for them.

“I think I feel alright, but baseball is baseball. You can feel great and then go out there and strike out five times in a row,”Rendon said. “It’s not that big of a deal if you get out. You just gotta go out there and take it one at-bat at a time.”

Rendon hit .287 with a .351 on-base percentage, 21 home runs and 83 RBI last season, and slots back into the top of the Nationals lineup which has not aligned as projected yet this season. Because of Jayson Werth’s broken wrist, the top of the order will not coalesce until later this summer, but Rendon provides a consistent on-base threat with power and speed.

“Well you can’t expect him to be the catalyst for anything right now, but we’re glad to have him back,” Williams said. “The fact that he’s physically able to play is important to us, and important to him as well. So he feels good. He’s got some at-bats. Not ideal amount of at-bats, but nonetheless he’s, like we said yesterday, he’s a pretty quick study. So we’re glad to have him.”

Rendon is in Thursday’s lineup at second base, where he played in 2013 before switching to his natural third base for 2014. Williams said to the extent the Nationals have an everyday lineup — injuries have caused constant erasures — Rendon will be the usual second baseman, and Yunel Escobar will play third. When the Nationals acquired Escobar this offseason, the plan was to play him at second and keep Rendon at third. Escobar is a natural shortstop, and made the transition to third smoothly when asked to fill in for Rendon. He did not get much work at second base, and so the Nationals will opt for Rendon, for now.

“Anthony has experience at second base, so he can do that,” Williams said. “And he’s gotten his reps during his rehab starts at second, too. So it’s an easier move for us to do for our club. I’m not saying it can’t change. But as of right now, that’s what we’re going to go with.”

Rendon said nothing surprises him anymore, so the move to second base did not unsettle him.

“I feel fine (at second),” Rendon said. “I’ve always told you I feel most comfortable with a bat in my hand. As long as I’m out here to help the team.”