Duke, who threw only one offspeed pitch during game, said fastball command was the reason he was successful on Tuesday.
"It was good. I wanted to go out there, be efficient, get outs. In a situation, [where I needed to step up], it felt good," Duke said.
Duke believes his success on Tuesday can carry over into the season. He is off to a slow start, allowing 18 earned runs in 20 innings.
"It's a work in progress. It will continue to work out. We are going to go forward from here," Duke said.
Bill Ladson is a reporter for MLB.com and writes an MLBlog, All Nats All the time. He also could be found on Twitter @WashingNats. Andrew Simon is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.