WASHINGTON -- This stint on the injured list was designed to give Sean Doolittle a breather, necessary after his right knee began bothering him while he was on pace for a career high in appearances. Yet, Doolittle has been keeping plenty busy -- and not just finishing several books on his reading list.

He is working out twice a day, trying to complete one session early in the day before his teammates who are active need the weight room, and then again right around the start of the game. He has thrown three bullpen sessions, each around 20-25 pitches, tweaking his mechanics to the point where he is starting to see his pitches appear crisper.

“I’ve been busy,” Doolittle said. “But it’s probably better than sitting around collecting dust.”

Doolittle is eligible to return from the IL on Wednesday, but he will not do so just yet, although he is preparing for what he called his final hurdle before returning. He is scheduled to throw a simulated game at Nationals Park on Wednesday, around 35 pitches, and if all goes well he could be activated from the injured list this weekend against the Marlins.

The Nationals are hoping this break can help Doolittle return to form. Before landing on the injured list, he acknowledged after multiple games that he was starting to feel the effects of fatigue, culminating in a disastrous five-game stretch from Aug. 9-17 when he gave up 10 runs on five homers in four innings (22.50 ERA) with two blown saves. It was part of a larger concerning span during which Doolittle allowed seven homers in 10 appearances before the Nats decided to shut him down.

“I kind of needed a mental break,” said Doolittle, who took about three days off from throwing after initially landing on the IL. “That two-week stretch there was really rough. All through that process, I was looking for answers. I was trying to find things and make adjustments and none of them were working. When you’re spinning your wheels like that, it’s kind of like a really helpless feeling.

“You’re searching for answers and you don’t really know how to fix it or where that fix is going to come from. To be able to pause and get my body right, it’s helped me a lot mentally as well. I’m in a much, much better place right now.”

Once Doolittle does return, he is expected to reclaim his spot as the club’s closer, a point on which Nationals manager Dave Martinez has not wavered throughout the process.

“Moving forward, Doolittle will be our closer,” Martinez reiterated on Tuesday. “I’ve said that before. This will be conversations that I’ll have with him; we’ll see where he’s at tomorrow and how he feels about everything tomorrow. I’m just waiting to see him pitch tomorrow and I hope that everything goes well, so we can have that conversation.”

Worth noting

• The Nationals placed reliever Hunter Strickland on the paternity list Tuesday after he flew home to Georgia to be with his wife for the birth of their second daughter. Catcher Spencer Kieboom was promoted in his place.

• Left-hander Roenis Elias, on the IL with a right hamstring strain, threw a bullpen session on Tuesday. He could also participate in Wednesday’s simulated game.