First, let's get the jinx disclaimer out of the way: This is only hypothetical at this point, can't count your chickens before they're hatched, that's why they play the games, etc.
But, hypothetically speaking, with an eight-game lead and the magic number at four, odds are in favor of clinching the division sometime this weekend. That leaves the Reds with somewhere around 6-7 games left to play.
Let's also grant that Philadelphia is going to win home-field advantage in the NL. The Braves are leading the wild-card race, let's say that is still the case first of next week. If the Braves win the wild card, then the Central or West winner with the worse record gets the Phillies in the Division Series.
The Reds have several guys who could use some days off to recharge before the playoffs. But if the Reds don't keep putting their best lineups out there in an attempt to outpace the NL West leader, they're on the hook to (probably) face the Phillies in the first round.
So how do you manage the last week looking ahead to the playoffs? The choices are rather clear, and I'll put them in a poll. Is your top priority having a rested team for the playoffs, even if it means facing the Phillies, or are you more concerned with winning and avoiding Philly, even if it means the guys who need rest won't get it?