I've seen some of the better cappers on here say over the years that it doesn't make sense to use the "avoid the sweep" logic to make a bet. I'd be interested to see if the stats on whether this strategy has worked over time. I remember in September, 2010 thinking there was no way the Cubs would sweep the Cards in St. Louis and thought about betting against them in the third game but Zambrano was pitching and he'd won 5 straight so I didn't bet it. Cubs won 7-3 for their first sweep in St Louis in 12 years.
I actually am shocked the Cubs won the first two against the Reds as I thought Jackson would get lit up. Samardzija has been average at best this year and was hit hard the last two times out. He has solid stuff though and is capable of a strong outing. I think the Reds probably do win but I'd probably take my chances on the run line rather than pay the big juice. Good Luck with the play. As a life long Cubs fan, you will eventually make money betting against them.