What is any of this?
If you don't agree that a yo-yo RP will cause trouble then you shouldn't be complaining about using Osuna in any particular situation. The win expectancy with a four-run lead drops if Tepera walks two guys to lead off the inning, which isn't a ridiculous proposition because he's awful, and then you have to use Osuna anyway to clean up the mess.
Expectancy for the Wild Card standings has way more variables and can't go wrong so quickly, but it isn't exactly stable either. I'm not comfortable with a "90%" Wild Card chance considering the Tigers get the Braves and the O's get the Yankees (and the Mariners get the A's FWIW) while the Jays get the Sox. That's why I think nailing down that 4-run lead was important, to get that win, and then deal with tomorrow as it comes. I'm not as confident in a playoff spot as you seem to think I am.