This idea comes from Doghouse over at Federal Baseball and it's really quite simple if you buy into Wins Above Replacement. Basically, the idea is to plug 2008 data for your favorite team into the easy-to-use WAR Spreadsheet and see how closely the team's talent matches their actual win total. It's not a prediction, it's a "post-diction".
This analysis is a bit different from something like Pythagorean record, because we're not dealing with actual runs scored. On offense, for example, we're dealing with either wOBA or OBP/SLG plus baserunning. Teams may have been lucky or unlucky in the way their batting events combined to score runs. And, like with Pythag, we're removing the timing of runs scored and runs allowed, which is not much of a skill beyond properly leveraging a bullpen (and leverage is included in the spreadsheet).
If you go ahead and plug in 2008 data and write something comparing "post-jected" wins to actual wins, let me know and I'll record the numbers here and link to your article. (It also will be a good test to see if the baseline win total used in the spreadsheet is accurate enough.)
Nationals: 59 act, 62 Pythag, 63 WAR spreadsheet
Mets: 89 act, 89 Pythag, 87 WAR spreadsheet
Twins: 88 act, 89 Pythag, 82 WAR spreadsheet