Not to be a wet blanket, but the numbers here are not right. At best, the '123' can represent our magic number vs. the Cards. (I haven't double checked the math, but assuming it is right.)
We also have a magic number vs. every other team in the division. Since the Cardinals are in second, our number vs. them is currently the highest. But it is quite possible for there to be a combined total of 123 Reds wins and Cardinal losses the rest of the year, and neither of those teams make the playoffs. What if the Cubs actually get hot, and pass up the Cardinals or the Reds? May seem unlikely right now, but there is a lot of baseball yet to play. Cubbies are only 5 or 6 games back.
Magic numbers really only work well toward the end of the season when you are down to two or three teams.
There are also several sites that do a 'playoff odds report'. This morning, before today's win, they listed the Reds as having a 34% chance of making the playoffs, and the Cardinals as having a 60% chance. The reason? Pythag records and win expectency based on pythag.
But I will say this: with how the Reds have been playing the last two weeks, it is hard to see them not having a really good chance to win the division. The Pirates, Astros, Brewers, and Cubs have looked terrible. The Cardinals look much better than the other teams, so it is natural to look at them as the only club that could beat the Reds.
But things do change and shift throughout the season.