CINCINNATI -- The Washington Nationals erupted for seven runs in the seventh inning and then watched in agony as the Cincinnati Reds came back with seven runs in the last two innings against a beleaguered bullpen to make it close.

Anthony Rendon hit two home runs, including his second career grand slam, and drove in six runs to back Max Scherzer's six scoreless innings in the Nationals' 10-7 win over the Reds on Saturday night.

"You never know," Nationals manager Dusty Baker said. "Rendon had another great game. You never knew the grand slam was going to be the deciding swing. Those guys don't quit. They have a good offensive ballclub."

Rendon was on base five times with a single and two walks for the Nationals (54-36). It was his third career multi-homer game.

Rendon did not make the All-Star team in spite of his presence on the National League leaderboard in on-base-percentage (.420), doubles (22), walks (51), batting average (.315) and slugging percentage (.582).

"I'll let y'all write about that," Rendon said. "I try not to think about being hot. As long as we're winning, that's all that matters. We're just trying to extend this lead and keep grinding."

The Nationals defeated the Reds (39-51) for the fourth time in five games.

Scherzer (10-5) escaped early jams but struck out 10 to extend his NL-leading strikeout total to 183.

"They put some good at-bats on me. They really grinded me out," Scherzer said. "We just kind of stuck to the game plan. We were joking in the dugout that Wieters had the best sequence he's had all season. Facing (Joey) Votto with runners on first and second and nobody out, your back's to the wall. If they were looking fastball, we went off-speed. If they were looking off-speed, we went fastball."

Scherzer allowed three hits and four walks in his first start after the All-Star break.

"Scherzer gave us all he had," Baker said. "He pitched in the All-Star Game, so we knew it was going to be a short outing — shorter than normal. He got out of those jams in the first and third."

Losing pitcher Luis Castillo (1-2), who picked up his first career win in his last start, worked six innings, allowing three runs, three hits and four walks.

"Castillo wasn't bad," Reds manager Bryan Price said. "He's been sharper, but he did a nice job against an outstanding offensive ballclub. It's another step in the right direction. He kept us in the game."

Castillo fell behind 3-0 to Rendon in the fourth inning.

"I wanted to challenge Rendon. I didn't want to walk him," Castillo said. "Sometimes when you get two quick outs, you think the job is done. The game is going fast but you have to make good pitches then too."

The Nationals broke the game open with a seven-run, seventh inning against Michael Lorenzen (six runs) and Blake Wood, who was greeted by Rendon's grand slam.

Ryan Raburn, who spent spring training with Cincinnati, led off the inning with his second home run since coming to the Nationals in a minor league deal with the Chicago White Sox on May 26.

The Reds scored five runs in the ninth against Trevor Gott. Three runs crossed on Scooter Gennett's 16th home run of the season.

Matt Grace entered after the Nationals' lead was cut to three with no outs and retired three straight batters for his second save.

Washington's Bryce Harper extended his hitting streak to 10 games with a one-out single in the fourth inning. Daniel Murphy, the All-Star second baseman, doubled to the gap in left center with two outs to score Harper. Rendon followed with a homer to give Washington a 3-0 lead.

The Reds put the leadoff man on base in each of the first three innings against Scherzer.

Billy Hamilton hit a ground-rule double in the bottom of the first. Zack Cozart walked, but Scherzer struck out Votto, Adam Duvall and Gennett.

Hamilton singled and stole his 39th base of the season in the third, but Scherzer fanned Votto looking on a 3-2 pitch. After Duvall popped to short, Gennett was Scherzer's eighth strikeout victim.

The Reds had a baserunner in each of the first five innings but failed to score against Scherzer, who struck out 10 to log his 12th game with double-digit strikeouts.

NOTES: RHP Joe Ross will have Tommy John surgery on his right elbow on Wednesday by Dr. Keith Meister in Arlington, Texas. Ross was placed on the the disabled list. ... Nationals OF Jayson Werth had a long meeting with manager Dusty Baker on Saturday afternoon. Werth has been on the 10-day disabled list since June 4. "He is doing what he can to stay in shape," Dusty Baker said. "He's a worker." Werth has been shut down from baseball activities for the time being. ... Reds C Devin Mesoraco was took batting practice on Friday and was scheduled to catch a bullpen before the game. "We didn't have anyone who needed to throw a bullpen," Bryan Price said. "We got an OK to let him warm up our pitchers who are coming into the game."