Nickel explaination of waivers

As requested by Dorf, here is a quick and dirty explaination of waivers as I understand them (note: therefore probably incorrectly):

MLB:
In-season -

In August, most players are put up on the waiver board by each team to free them up in case they want to be traded.

When a player is put on waivers, any team that is interested in the player can put a claim to them. The two teams then have a window of time to hammer out a trade for the player, or else the original team can pull the player back (meaning the player will not be traded to any team). If more than one team claims the player, then the team with the worse record gets the claim (confusing caveat: this only applies within the same league. For example, if Dontrelle Will were put on waivers in the NL, the Cardinals-NL team- could claim him before the Devil Rays-AL team- even though the Rays have a worse record. However, the Devil Rays could claim the before the White Sox-also an AL team- because the Rays have a worse record).

If the player passes through waivers without being claimed, then the player is free to be traded to any team without restriction. However, most trades of this sort occur on or before August 31, because a player must be on the roster before September to be eligible for the playoffs.

Designated for Assignment -

This is an irrevocable move by a team on a player who either has no more minor-league options left or has been in the majors for too many seasons (I believe the 4th season requires this). The team then has 10 days to trade the player without restriction. If they don't trade them in the 10 days, then the player can opt to either accept a minor league assignment or become a major league free agent. Regardless, the original team pays the rest of the contract. If the player signs on elsewhere, however, the old team only pays the balance of the contract the new team doesn't cover. This is why a DFA'd player will usually sign for the veteran's minimum, because the new team gets the player cheap while the player still gets the same salary while also still forcing the old team to pay the bulk of their contract.

Off-season waivers -

There are a few strains of these, many of which I don't understand. Irrevocable waivers (what Manny was put on after '03) allows another team to grab the player without having to trade anything; they just have to cover the rest of the contract. I believe regular waivers in the off-season operate the same as the in-season ones described above.

NFL:
Fortunately, the NFL really only has one type of waiver (that I know of). Basically, whenever a team cuts a player, they are actually just putting them on waivers. Each team then has a chance to claim the player based on the standings from the last year's draft order (so the 49ers get the first crack at every player, the Pats the last). The old team doesn't have to pay any part of the salary, though they do still have to account for salary cap money that was already paid (unamortized portions of the signing bonus, for example). I believe that a team that claims a player must assume the old contract, however. Teams can also claim the players off waivers to their practice squad, though the player does not have to accept that. If the player clears waivers, he may then sign with any team (active roster or practice squad) that he chooses, including the original team that cut him.

Next logical question: how does this affect the salary cap?

Cut before June 1 - The rest of the signing bonus/gauranteed money that has not been accounted for in the salary cap hits the next season. For example, Ty Law was cut last spring, and still had some of his signing bonus unaccounted for (1/7th of the original bonus). That money, in it's entirety, is counted against the Patriots cap this year; basically, any money paid to the player that hasn't been caught in a previous year's cap will hit the next year. This applies to traded players as well (which is probably why T.O. wasn't traded, as 5/6th of his signing bonus hasn't been accounted for yet).

Cut after June 1 - The rest of the signing bonus/gauranteed money is put half on the coming year's salary cap and half on the next year's cap. This is why a team can still carry "dead money" from a player so far into the future (for example, the Pats had charges from Lawyer Milloy on the cap during the 2003 and 2004 season, even though he was cut before the first game of 2003; he is entirely off the books now, though).

Roster bonuses - Obviously, teams in dire cap position often want to opt for the later of the two types of cuts (that is, after June 1st). However, players that are cut after June 1st tend to get smaller contracts with their new teams later in free agency, so they would prefer to be cut right after the season ends. This is why some players insisnt on large roster bonuses in the spring, because it forces the team to decide whether to keep a player or cut him earlier.