One of the biggest developments in sabremetrics has been quantifying the number of wins an individual player contributes beyond the average bench player.
Stats like WARP (and it's derivative WARP3), Win Shares, and (to a lesser extent) Win Probability Added (WPA) all take this approach.
Click the links for further reading on WARP3, Wins Shares, and WPA.
One fo the things that has been troubling me about all the posturing over Arod, and the talk of losing Mo and Posada over Torre has been how much we can reasonabily expect their replacements to pick up the slack.
Check out what Jeff Sackman over at The Hardball Times has to say about it.
For teams with $150+ million payrolls every year, free agent math works differently. Those last several marginal wins, getting them from a projected 88-90 win club to a projected 95-100 win club, are way more expensive than the rest.
The biggest problem, when it comes to putting a 95+ win team on the field this year, is how to get all those wins into the lineup. There are only so many free agents out there, and there are only so many places to put them.
After Arod, the best Yankee options seem to be Mike Lowell or a trade for Aramis Ramirez (I'll have to think about that; depends on the trade package).
Either one of those guys is a 5 win drop off. So we're down to 89 wins even with an All-Star replacement.
We discussed Torrealba as a Posada replacement in passing the other day. He'd come within 4 wins of Posada's production. Now we're down to 85 wins even with the best available Free Agent replacement.
Then we get to Mo, whose value is the toughest to qualify because of the young arms lurking in the wings and the chance of a reliever putting together an unexpectedly good season (see Okijima).
Baseball Prospectus figures that Mariano was 3.6 Wins Expected Above Replacement. Joba's short stay in the pen registered a 1.8. Let's call the difference between Rivera and his replacement 2 games (I think that's generous).
So we're down to a 83 win team.
If we lose free agents 1A, 1B, and 1C, we're going to ask the pitching staff to be 12 wins better than they were this year.
Take some time to digest this. Ask questions. When I get home from work, I'll share with you my projections for next year's rotation.