Toni L. Sandys/TWP Toni L. Sandys/TWP

Bryce Harper returned to the Nationals’ lineup tonight after missing the previous two contests with swelling in his left knee. Harper tested the knee in the outfield this afternoon and determined he could play on it, although swelling and bruising remains from his collision a week ago with the fence at Dodger Stadium.

“It’s something that you don’t like doing, run into a wall at 100 miles an hour,” Harper said. “You’re going to feel something this day, feel something that day. I’m just trying to keep up my knee and see what happens.”

Harper played two games last week after the collision. He found the pain, which also came from a bruised abdomen and shoulder, did not compromise at the plate or in the field – in one at-bat, he smashed a 431-foot homer to dead center. But he still feels the effects.  Sliding, he said, could be particularly problematic.

“It was more just running on it and sliding, things like that,” Harper said. “If I need to slide, it’s probably going to hurt worse. If I bang it up or something, I’ll be right back to square one. Hopefully I don’t do that.”

The Nationals did receive some good news health news today. Starter Ross Detwiler felt significant improvement with the slight oblique strain that prevented him from making his start tonight. If he continues to make similar progress in the next few days, he expects to make his next start, Sunday at Nationals Park, on schedule.

“Today was one of those really positive days,” Detwiler said. “There was that much progress last night. I feel very good about today.”

Detwiler rode a stationary bike this afternoon, and he plans to play catch tomorrow. He said the oblique strain is “still there,” but that another day like today should keep him on schedule.

The Nationals do not plan on placing him on the disabled list, but they may still make a roster move to bolster their roster. Depending on how Zach Duke performs tonight, and how many innings he logs, the Nationals may add a reliever from Class AAA Syracuse. In that case, they would carry an extra reliever and send down one of their bench players, most likely outfield Eury Perez.

With veteran J.C. Romero on the disabled list at Syracuse, the most likely candidate to be called up would be lefty reliever Fernando Abad, who has a 1.06 ERA in 17 innings.