Arroyo and the Nats' Jordan Zimmermann are the scheduled starters in the second game of four at Nationals Park.
Arroyo was sharp through six innings in his first start of the season against the Marlins on Sunday, but things started to unravel in the seventh. His final line was four earned runs on 10 hits and no walks with four strikeouts in 6 1/3 innings.
"For me personally, other than the seventh inning, I was happy with the way I went out and threw strikes," Arroyo said. "I commanded every pitch, kept my pitch count down and pretty much did what I wanted to do all day. Sometimes you open up a can of worms. I hit [Greg] Dobbs there to lead off the seventh and sometimes you can't put the lid back on that thing."
Arroyo ended up with a no-decision in the Reds' 6-5 win.
Zimmermann was tagged with a loss in his first start, a 4-3 Nats loss to the Cubs on Sunday, but he pitched better than Arroyo. He allowed one earned in seven innings, also walking none and striking out four. In the fourth inning of the Cubs game, Zimmermann was hit on the right hamstring by a line drive off the bat of Darwin Barney, but he remained in the game.
The Nationals capitalized on game No. 1 of 11 in a row at home Thursdat on an Alfredo Simon wild pitch that scored Ryan Zimmerman, giving Washington its third consecutive victory.
Reds: Phillips still a maybe
Battling a sore left hamstring, second baseman Brandon Phillips was unavailable for a third straight game Thursday in temperatures that weren't exactly warm.
"He'll come in probably lobbying, probably smiling," manager Dusty Baker said. "I'm guessing maybe Saturday or Sunday maybe. It's supposed to warm up those two days."
Nationals: Outfielder Morse out for six weeks
Michael Morse is expected to be shut down for six weeks after aggravating his strained right lat (back) muscle Monday in a rehab game with Class A Hagerstown.
Morse can swing the bat without any problems, but he continues to feel discomfort while throwing. There is no surgical option.
"We are going to put him on total shutdown mode for six weeks, so he can rest it," Nationals general manager Mike Rizzo said. "We'd tried to ramp him up and get him ready as quickly as we could, because he is a big piece of our lineup. He just reaggravated it, and we have to be ultra-cautious and make sure he is right for the majority of the season."
Reds reliever Ryan Madson had successful Tommy John surgery to repair the torn ulnar collateral ligament in his right elbow on Wednesday. Dr. Lewis Yocum performed the surgery in Los Angeles.