Dunn, who is a free agent after the season, has been mentioned in trade rumors for weeks. He has been linked to the White Sox and Angels, who need a power bat. However, Zimmerman believes Dunn should stay as a member of the Nats and hit homers for them.
"Obviously, he is one of the best [cleanup hitters] in the game -- has been for the last five or six years," Zimmerman said. "I think he is a very important part of this team as far as what we do offensively -- not only on the field, but in the clubhouse as far as helping out the young guys. He is really, really a big part of this team."
Dunn was a big part of the game on Wednesday. He became the second player in team history to hit three home runs. The last member to accomplish the feat was Alfonso Soriano, who did it against the Braves on April 21, 2006.
The game was tied at 1 in the first inning when Dunn took right-hander Jon Garland's 1-0 pitch and hit a three-run homer over the center-field wall.
"Dunn is a prolific home run hitter," Padres manager Bud Black said. "It's what he does. You make a mistake, at times, he will make you pay."
Two innings later, after San Diego cut the lead to 4-2, Dunn took the first pitch from Garland and hit his second blast over the left-center-field wall to give Washington a three-run lead. Garland would give up another home run, this time a solo shot to Ian Desmond.
The winning pitcher was J.D. Martin, who lasted 5 2/3 innings and allowed two run on six hits to pick up his first victory of the season. After getting two quick outs in the sixth inning, Martin allowed two singles to Chase Headley and Nick Hundley. Martin was then taken out of the game.
He was upset that he left the game. However, he realized that had he fielded the ball cleanly off the bat of Headley, it would have been the third out of the inning and he would have possibly pitched an extra inning.
The Nationals relievers made it an interesting game in the seventh and eighth innings as Joey Peralta and Drew Storen allowed a combined three runs to make it a 6-5 game before Dunn came to the plate in the eighth and hit his third home run of the game on a 2-2 pitch off left-hander Joe Thatcher.
About a minute later, Dunn received a curtain call from the Nationals fans.
"It's pretty cool to hit three home runs, but I think the last one -- since we won -- was the biggest," Dunn said. "I don't feel any different than I have in the past. I got pitches to hit tonight and didn't foul them off like I have been doing. It was a pretty cool deal. The main thing is to, obviously, win."
Asked how he felt about getting the curtain call, Dunn said, "It just shows that the fans are into the game. It means a lot when they acknowledge something that doesn't happen everyday. It's a great feeling."
The third homer turned out to be the game-winner, because closer Matt Capps allowed a pinch-hit homer to Matt Stairs to make it a one-run game. It was Stairs' 20th career pinch-hit blast, which ties a Major League record.
With the victory, Washington won its 38th game of the season. With a little over three weeks left until the non-waiver Trade Deadline, the Nationals players are aware that they have to start winning, because they don't want to see the team break up.
Dunn said he doesn't consciously think about the breakup of the team -- and for a good reason.
"You don't consciously think about it, because all you try to do is win every single game," Dunn said. "I don't care if we are 50 games out or up 50 games. What matters is winning the game. All that [Trade Deadline stuff] is out of our control.
"We can't go out there thinking, 'If we don't play well, we are going to get traded.' We can't do anything about that as players."
If the team decides that a change is in order, Dunn will likely be one of the first to be traded. Josh Willingham is another teammate who doesn't want to see Dunn depart.
"Who doesn't need a 40-home run, 100-RBI guy," Willingham asked. "He hit 38 last year, two short of 40. How many years in a row did he hit 40 home runs and knock in 100 RBIs? Basically five years in a row he has done that. So he is pretty invaluable to the team."