Today's game will determine whether the rest of the games this season are meaningful. A win and they are 3 back with 20 left. A lot different than being 5 back with 20 left.
Let's say the Cubs go 12-8 the rest of the way after today. That's slightly better than their season record. 15-5 would be enough to tie and would be very tough but doable. 17-3 is very unlikely.