Not anymore than you can look at Run Differential an"projections" and call it a day. With regard to projections, am I to presume you are insinuating the name is a misnomer by putting it in quotations? People need to stop assuming that all "projections" are based on crazy, seemingly arbitrary math. There are certainly some questionable ones out there that should be more heavily scrutinized but the simplest projections (like Marcels) basically do what every fan does intuitively when trying to use stats from prior seasons to guess on future performance: 1. Look at previous years' performances, weighing the most recent seasons more. 2. Regress to the mean, with the amount proportional to the amount of AB or IP the player has (we can trust the stats from a guy who has 1,800 AB over the last 3 seasons more than one who has had only 50 AB). 3. Adjust for age (a 25 year old should be expected to get better, a 35 year old is probably getting worse). Obviously, we shouldn't stop there, however. If we know more about a player (scouting information for a young prospect and recent injury history being the big two), we should also consider that. I'm not going to change my expectations for Gabe Kapler just because he says he has a new swing, though. With regard to run differential, it certainly isn't the end all, be all, but when a team wins a lot of games with a negative run differential, something is up. A team will do that for a season from time to time, but none can keep it up year in and year out. As a result, we should be very suspicious of any projection that uses Seattle's 2007 record as a jump off point.