There is a chance the Guardians could catch the Astros, meaning the Red Sox would play the Astros in the first round and the Guardians would play the wild card winner. I like this scenario better--going into Cleveland again, without home field, in a 5 game series, doesn't seem very promising for the Red Sox. Sale struggles against the Guardians and Kluber is Kluber.
Of course, all of this assumes the Red Sox will win the AL East, which is now far from certain.
Let's say the Yankees win the division. The Red Sox use C.Sale in the wild card game and the winner most likely plays the Astros, assuming the Guardians don't pass the Astros. In a weird sort of way, I like this scenario better than a 5 game series against Cleveland (with Cleveland getting home field). If the Red Sox win the W.C. game, they would take on the Astros with C.Sale unable to pitch game one. Another starter would have to step up.
The Astros are a problem for the Red Sox, though. The Red Sox don't hit lefties and would likely face D.Keuchel twice. That's trouble. The Red Sox just don't have the feel & look of a championship team this year--too many guys having down years, too many injuries as well. And I'm not sure J.Farrell has done a good job managing and pacing C.Sale. The most important games are in October and I'm worried Sale might not have enough left in the tank to be dominant in October.