"There's no time to sit back and see what you've done," Nationals manager Dusty Baker said. "You got to think about after you've done it, then you try to improve on it and do it. I think about the games that got away that we should've won is the way I look at it. And when things are going good, you get greedy."
Zimmerman's two-run homer to left-center field in the fourth inning was his 13th of the season, which ties the Yankees' Aaron Judge for the most homers in baseball. He nearly had one more, but Phillies center fielder Odubel Herrera jumped to catch a ball at the center-field wall in the second.
Rendon hit a three-run homer to left field in the sixth to give the Nats a 6-1 lead. Rendon, who went 6-for-6 with three home runs and 10 RBIs on Sunday, finished the seven-day stretch with three doubles, five home runs and 17 RBIs.
"It's almost this whole lineup is kind of like, I don't want to say competition, but we each push each other," Zimmerman said. "And you want to continue to get hits so you can keep up with everyone else."
Phillies right-hander Vince Velasquez was cruising through five innings before allowing four runs in the sixth. He gave up seven hits, six runs and struck out eight in seven innings. After an 11-9 start, the Phils have lost eight of their last nine games and five straight.
"When things aren't going your way, everything seems to happen," Phillies manager Pete Mackanin said. "It snowballs. It's not fun to lose five in a row."
MOMENTS THAT MATTERED A.J. is OK: The Phillies hit some balls hard against Nationals starter A.J. Cole, but he limited the damage in his season debut. Cole allowed six hits, one run, four walks and struck out two in six innings. It helped that the Phillies made three outs on the bases with a batter's interference call in the first, Tommy Joseph getting thrown out trying to stretch a single into a double in the second and Michael Saunders getting caught stealing in the fourth.
"I was always fighting the whole game, really trying to get ahead of hitters and throw strikes," Cole said. "And a lot of times, I was getting behind, which made it pretty difficult for me. But like I said, you have the defense behind me making plays, which also made it easier. It helped me settle in a little bit."
Rupp heats up: The Phillies would have been shut out, if not for Cameron Rupp. He singled to score the game's first run in the second inning. He then homered to right-center field in the seventh. Rupp is hitting .385 (10-for-26) with three doubles, two home runs and three RBIs and a 1.197 OPS in his last seven games.
"I'm comfortable," Rupp said. "I'm being selective and I haven't missed my pitch. I'm not fouling them off like I was the first few weeks. I'm making good contact. I wasn't worried about what was going on. And now that I'm swinging the bat well, I'm gaining confidence and will continue to go."
QUOTABLE "That ball was directly in the lights. He's been playing super defense for us. What a shame that was. That led to something." -- Mackanin, on right fielder Saunders losing a ball in the lights in the sixth inning, leading to Zimmerman's double. Rendon followed with a three-run home run.
ODUBEL ROBS ZIM According to Statcast™, Zimmerman's batted ball to deep center field in the second inning had a 77 percent Hit Probability, but Herrera jumped to catch it at the wall. Similarly hit balls are home runs 67 percent of the time.
Herrera said afterward he did not know if he robbed Zimmerman of a home run, or if it would have hit the top of the fence.
"It was close," he said.
WHAT'S NEXT Nationals: Right-hander Tanner Roark (3-1, 4.04 ERA) will take the mound for Sunday's series finale against the Phillies at 2:35 p.m. ET. Roark extended himself to a career-high 125 pitches in his last outing, so the Nats plan to manage his pitch count.
Phillies: Right-hander Jeremy Hellickson (4-1, 3.18) hopes to return to form on Sunday against the Nats. He suffered his worst start of the season on Tuesday against the Cubs at Wrigley Field, allowing six runs in four innings. Hellickson had not allowed more than two runs in any of his first five starts. He has allowed just five hits and two runs in 12 innings this season against Washington.