Because a good pitcher on a bad team can make them a good team for a night, or in the case of a a great rotation, almost every night. In the early to mid part of the season, you could make a decent argument that the Nats weren't very good offensively, you could make a better than decent one, actually. Even bad teams are going to put up two to three runs on most nights. If you've got the pitching at the level of what the Nats got the first half of the season where they were only giving up a couple of runs a game, then you're going to keep yourself in every game, even with a bad offense and the Nats offense was just good enough to get one more than the other guy, but that was because their pitching was very good to dominant nearly every night. Now, if you take out Gio and JZimm for, say a month each, and replace them, even with Lannan, who's serviceable and to good with an occasional outstanding night, you're going to see guys who give up three to five runs a game. That wouldn't have been good enough in May and June. Once everyone got back and was healthy again, you saw the offense substantially improve and that was when you saw the Nats pull away. If you've got the rotation the Nats have put together and they stay healthy, that can mask a lot of the issues the offense went through early in the year. That wouldn't have been the case, at least not night in and night out if it was the other way around.
You're right. I would choose a kickass and healthy rotation over a kickass and healthy lineup simply because the former is harder to replace. But it's not like we need to go into next season expecting the injury bug to simply tradeoff. It would be unreasonable to expect several of our top starters to miss multiple months to injury. I don't expect all five starters to make 30 starts next year but I'm not expecting another extreme either.
