After rallying to beat the Pirates, 9-7, on Thursday, Milwaukee has won five straight and 23 of its last 29 games to climb within 2 1/2 games of St. Louis, which currently holds the final playoff spot in the NL.
The Nationals, meanwhile, are in a playoff race of their own. They clinched Washington's first trip to the playoffs since 1933 with a 4-1 victory Thursday night against the Dodgers. But they are still aiming to hold off the Braves and win the NL East.
"The only thing that means anything to me is when we clinch the [division]," manager Davey Johnson said. "That's the only thing I'm concerned with.
"Whatever number that is, it will be my favorite number."
Washington, which leads Atlanta by 5 1/2 games, has a magic number of eight.
Because the Nationals are still in a playoff fight even with their win Thursday, Roenicke said it doesn't matter to him that his opponent already has clinched a playoff spot heading into the opener.
"With the scary thing in a one-game [Wild Card playoff], they've got to try to win the division," Roenicke said. "So, no, that one game doesn't matter at all. Now, if they clinched and won their division, that would be different."
Right-hander Shaun Marcum will start Friday for the Brewers. It will be Marcum's sixth start since returning from elbow tightness that landed him on the disabled list for two months. He has allowed 15 earned runs in 23 2/3 innings since returning, but at this point in the season, all the Brewers care about is getting a victory.
"For us, obviously, we need to win every game, every time," first baseman Corey Hart said.
The Nationals will turn to right-hander Edwin Jackson, who has had a rough September. Jackson has allowed 14 runs in 15 2/3 innings in three starts this month. Still, he will be bidding to become the fifth Nationals starter with at least 10 wins.
Brewers: Aoki's strong rookie campaign
Right fielder Norichika Aoki extended his hitting streak to 10 games with a leadoff single on Thursday. It is the fourth time this season Aoki has had a hitting streak of at least 10 games. The last NL rookie to have so many 10-game hitting streaks in one season was Cardinals outfielder Bake McBride in 1974.
Aoki, who played for seven years in Japan before signing a two-year deal with the Brewers in the offseason, is hitting .293 with a .362 on-base percentage and 28 stolen bases this season. Manager Ron Roenicke made the case for Aoki in the Rookie of the Year race.
"I don't think of him as a rookie, but I understand the difficulty in coming over here your first year, trying to adapt to everything," Roenicke said. "That's hard, to put that on a player. He's got to perform, but he's got to adapt to everything we do. I think that's an important thing to consider."
Nationals: First team to 90 wins
With a 3-1 victory in the first game of Wednesday's doubleheader against the Dodgers, the Nationals became the first team in the Major Leagues to win 90 games this season.
It was the first time the franchise won 90 games since the Expos won 94 games in 1993, and the first time a team in Washington had done so since the Senators won 99 games in 1933.
The Nationals are still hoping to win the franchise's second division title and the first in Washington since 1933.
Marcum has only pitched against the Nationals once. As a member of the Blue Jays, he allowed two runs in seven innings and struck out a career-high seven batters in a 7-3 victory on June 16, 2007. Only two Nationals who played that day are still with the club -- third baseman Ryan Zimmerman and catcher Jesus Flores. Hart and second baseman Rickie Weeks have each hit three home runs and a double off Jackson in their careers.