The matchup to finish the season series instead will be Gio Gonzalez vs. Jon Lester, with Scherzer and Arrieta not making their next starts until Monday, when the Nationals will be hosting the Marlins and the Cubs face the Giants at AT&T Park. Why the change?
The first thing that comes to mind is the teams are being cautious about giving each other another look at their big right-handers because they're almost certain to meet in the best-of-five NLDS if the Cubs hang on and win the NL Central. But that's not it.
Arrieta got pushed back because Joe Maddon has been using Lester every fifth day coming out of the All-Star break, which caused him to move ahead of Arrieta the last turn through the rotation. The Nats give Scherzer at least one extra day off because he left his last start with a stiff neck, supposedly because of an uncomfortable hotel pillow.
Maddon says there's too much time left in the regular season to start manipulating his roster and his decision-making because the Cubs seem like they are headed to an October matchup with the Nationals. He says he's going to do everything he can to win every game, even if it means tipping his hand on a safety squeeze bunt or some other strategy he could use in the postseason.
"I think it's too early to nurture that type of thought for me,'' Maddon said. "It's just, 'Let's go play.' I'm sure [the Nats] would feel the same way.''
The teams split four games in Washington in late June, with the Cubs short-handed while Jason Heyward, Ben Zobrist and Kyle Hendricks recovered from injuries. The Cubs would love a sweep this weekend because it would widen their lead in the NL Central and cut into the current 6 1/2-game gap behind the Nationals, signaling a run for home-field advantage in the NLDS.
It should be a fun weekend. Here are the top 5 things to watch:
1. Is it possible that Nationals third baseman Anthony Rendon is really the best player on the field?
These are glittering rosters, with the Nats built around Bryce Harper, Daniel Murphy and Ryan Zimmerman and the Cubs countering with the Bryzzo brothers (Kris Bryant and Anthony Rizzo). But Rendon, who is in his fifth season and has never been to an All-Star Game, has the highest WAR on the two rosters (4.9 per Baseball Reference).
Rendon has been worth +6 Defensive Runs Saved this year (5 better than Bryant) while hitting .314./.419/.578 with 21 home runs thus far, matching the career high he set in 2014. He's on a roll, having gone 20-for-55 with five homers and 12 walks in 17 games since the All-Star break.
2. Can the Nationals match the Cubs' bullpen?
General manager Mike Rizzo attacked an obvious weakness by importing Sean Doolittle and Ryan Madson from the A's on July 16 and then adding Twins closer Brandon Kintzler in a move that Rizzo says was made "extremely close'' to Monday's Deadline. Rizzo was close to adding lefty Justin Wilson from the Tigers on Sunday night, but it was Theo Epstein who closed the deal.
Unlike a year ago, when the Cubs paid heavily for Aroldis Chapman, they were dealing from a strength. Maddon's bullpen ranks second in the NL in ERA and won MLB.com's "Bullpen of the Week'' metric for June 23-30. The Nats did get to closer Wade Davis for two runs on June 26, but it's their bullpen that still bears watching. Kintzler has never been in a spotlight quite like the one that will be on him the rest of this season, but he has to be feeling good after throwing 1 1/3 scoreless innings in his Washington debut.
3. Harper getting a chance to change games
Maddon famously implemented a strategy against Harper in May 2016 that led to a record-tying six walks in one game and 13 in a four-game series, four of which were intentional.
"Zimmerman was hitting behind him and was not having the season he's having right now,'' Maddon said. "The dynamic is more about the guy sitting behind him for me. … Last year I did all that stuff based on [the fact that] Ryan was struggling at that time. That was it. If Murphy was hitting behind him, I probably would not have done it at that time.''
Harper returns to Wrigley Field in a slump, as he's 2-for-21 in his past six games. Look for him to see a lot of Mike Montgomery, Brian Duensing and Wilson.
4. Dusty Baker as an improv artist
This time around it's the Nationals who are beaten up, with Trea Turner's broken wrist the biggest development since the teams met in Washington. The shortstop rattled the Cubs (Arrieta and the since-traded Miguel Montero, especially) by stealing seven bases in that series, but he is currently at the team's complex in Florida, working his way back toward a return later this month.
5. Can the Cubs continue to play like it's 2016, not like they were for the first half of this season?
This is the Cubs' time of year. They've gone 84-37 after July 31 under Maddon and seem to believe they are capable of that same roll this season, possibly winning 95-plus games for a third straight season. They'll have to turn it up hard in order to do that after their 43-45 first half, but it's possible.
Epstein says the dynamic around the Cubs is completely different than it was before the All-Star break.
"It's kind of a chicken-and-egg thing,'' he said. "Because you're winning, is there fun around the team? Or are you winning because the fun is back? We don't know, but we know we came together. It's been fun to watch our players take control of [getting] their season back, re-establish a certain feel around the team that we think is important.''
Phil Rogers is a columnist for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.