I agree, I did feel that at times leading up to the season people acted as if the Red Sox's starting rotation was a given, when in fact (as you pointed out) it's definitely up in the air. But everyone has question marks, and the Red Sox still have one of the best, if not the best, roster in the American League.
You're never as bad as you look look when you're playing poorly, and you're never as good as you look when you're playing well. It's easily to focus on the flaws when things aren't going well, but it's just eight games and I think this will all be forgotten when the Sox inevitably turn it around.