In the top of the fourth, Washington second baseman Daniel Murphy plated Bryce Harper on a two-out double for the opening run of the game. Rendon followed by turning on a 97-mph fastball from Reds starter Luis Castillo and driving it into the seats in left-center to push the lead to 3-0.
"I made a mistake, and he's a really good hitter," Castillo said. "You can't make a mistake with him."
When he stepped up in the seventh, the previous five Washington batters had all reached base. On a 1-2 changeup from Cincinnati reliever Blake Wood, Rendon lifted the ball over the wall in left-center to clear the bases.
It was Rendon's second grand slam of his career, and it also marked his third multi-homer game of the season.
"We like having him behind Murphy, Because you know Murphy's going to be on base a lot, and the hitters preceding Murphy are going to get on base a lot," Baker said. "So that's a lot of opportunities for Anthony. And we feel good, the middle of our order, they've all got 60 RBIs. They're all hitting .300. They're carrying most of the weight on this team."
In the first half of the season, Rendon hit .304 with 16 home runs and 54 RBIs, but finished fourth among NL third baseman in All-Star voting. He was a candidate for the All-Star Final Vote, but fans ended up selecting Dodgers third baseman Justin Turner instead.
He's hitting .483 in July, and has reached base in 12 of his last 14 plate appearances. Still, Rendon laughed out loud when asked if his recent success was revenge for his All-Star snub, and remained sardonic when trying to explain his recent successes.
"I think just when the pitcher throws the ball over the plate, I just try to put the fat part of the bat on it, and it happens to go into the stands or hit grass, and then I get on base," he said. "I don't know."
If Rendon keeps his current pace, he could set new career marks in hits, doubles, home runs, RBIs and batting average this season. And whatever the cause may be, 2017 is shaping up to be a very successful year for Rendon and the Nationals.
Jeremy Vernon is a reporter for MLB.com based in Cincinnati and covered the Nationals on Saturday.