DENVER -- The Nationals have decided that right-hander Livan Hernandez will pitch on three days' rest against the Mets on Wednesday night at Nationals Park.

The Nationals were thinking about calling up a Minor Leaguer for that game, but after throwing 100 pitches in the first game of a day-night doubleheader against the Rockies, Hernandez went to manager Jim Riggleman's office and volunteered to take the ball.

"Livan said, 'Hey, you are going to probably need a pitcher Wednesday. Let me pitch that day,'" Riggleman said. "We picked him, and he volunteered for it at the same time. So somebody is going to pitch that day."

Washington needed a pitcher Wednesday because the day-night doubleheader messed up their rotation plans. Hernandez was originally scheduled to start Friday against the Rockies, but the game was postponed because of rain, and he had to pitch Saturday instead.

Hernandez said pitching on three days' rest is nothing to him.

"One hundred pitches is nothing. I threw 85 pitches [in the bullpen] before Saturday's game started," Hernandez said.

Dunn scratched; Morse gets start at first

DENVER -- Nationals first baseman Adam Dunn was scratched from Sunday's lineup because of flu-like symptoms. Dunn is one of the hottest hitters on the Nationals, going 10-for 29 (.345) with three home runs and six RBIs in his last seven games. Two of those homers were hit at Coors Field during Saturday's doubleheader.

"Adam came in not feeling well, nauseous and so forth," manager Jim Riggleman said. "He didn't have a lot of energy today."

Instead, Mike Morse was in the lineup playing first base. Morse was activated from the 15-day disabled list before Sunday's game after the team designated Willy Taveras for assignment. Morse was at Triple-A Syracuse on a rehab assignment.

Morse hasn't played in the big leagues since early April because of a left calf strain. During his rehab stint, Morse was hitting .265 with three home runs and eight RBIs.

"It took a whole lot to get back to the Major Leagues, but I'm back, and I'm 100 percent healthy," Morse said. "I got a lot of games in, and I'm ready."

Morse will be a right-handed hitter off the bench. He could be a right-handed platoon with Roger Bernadina in right field, while spelling Dunn on occasion at first base.