"I thought Dan Haren did a nice job," manager Mike Redmond said. "He threw a lot of strikes."
A former member of the Nationals, Haren still has friends on his new division rival. Washington also started its ace, Max Scherzer -- Haren's former teammate in Arizona.
The Marlins' catcher on Tuesday was Jeff Mathis, who was with Haren years ago with the Angels.
"I threw to Jeff today," Haren reminded. "I threw to him when I was back with the Angels. We've had a lot of success together. He's really familiar with the way I throw, the way I attack hitters."
Although they were rival starters on Tuesday, Haren is glad Scherzer was able to sign his seven-year, $210 million contract with Washington.
"I go farther back with him," the Miami right-hander said. "I was with the Diamondbacks with him. I was happy that he got what he deserved. Spring Training is just fun for those reasons. I have a few friends over there with the Nationals. Getting to face guys that I know is fun, too."
It may just be his second Spring Training start, but the way Haren was hitting his spots with a fastball in the upper-80-mph range was encouraging.
"Things are progressing," Haren said. "I was a little more crisp today. The ball was coming out a little bit better. I've still got a ways to go. Obviously, the results were good. That's always a positive. I'm feeling good. I'm definitely moving in the right direction.
"My stuff is not as overpowering as other guys we have on the staff or some of the relievers we have. It's a little bit more difficult for me to just go out and work on things, because that could turn ugly quick."
Haren isn't reading too deeply into the results, especially since the Nationals didn't bring many of their regulars.
"It's a fine line you've got to walk," he said. "You're not going to throw to them exactly like you would pitch to them in the season. But then not doing that is a good recipe for giving up a lot of runs."
Joe Frisaro is a reporter for MLB.com. He writes a blog, called The Fish Pond. Follow him on Twitter @JoeFrisaro. This story was not subject to the approval of Major League Baseball or its clubs.