S Jermaine Phillips is one of five Buccaneers who became unrestricted free agents on March 5

We're just getting started.

The NFL's 2010 free agency period officially began last Friday, and the first weekend of activity was roughly similar to previous seasons: a few big deals in the early hours of the open market; a dozen or so players switching teams; a few trades thrown in to spice up the action.

But as highly anticipated as opening day of free agency is every spring, it is the beginning of a marathon, not a sprint. More than 500 players became free agents of some stripe when midnight struck on Thursday, and if this year's activity follows the pattern of the last decade or so, about a quarter of those men will switch teams at some point before the market closes on June 22. A good chunk of those moves will occur this month, another wave will take place before the draft and still more players will find new homes after the draft, when teams have a more defined sense of what they still need.

Of course, there is reason to believe that this year's free agency period will not be exactly like those that have come before. Because the current collective bargaining agreement has entered its final year, a number of changes to the free agency system have kicked in for this offseason. Most notable among those changes are the absence of a salary cap and the need for players to complete six accrued seasons, not four, in order to become unrestricted free agents.

That latter rule change affected free agency before it even began, shrinking the pool of available unrestricted free agents and sending roughly 200 extra players into the restricted free agent category. Since restricted free agents, as the name implies, are more limited in their ability to switch teams, there may be less overall team-to-team movement in 2010. On the other hand, the wash of coveted, in-their-prime players into the restricted pool may prompt teams to more aggressively pursue players in that category this year. Last year, not a single restricted free agent switched teams; though that was the first time that had happened in the 17 years since the first CBA, no more than eight restricted free agents have switched teams in a single offseason, and the number had hovered between one and four over the past five years.

The difference in this year's system is reflected in the Bucs' own class of free agents. Last year, Tampa Bay had 13 players who became unrestricted free agents at the start of the period, and just one who was restricted. This year, the Bucs' list of restricted free agents was officially one player longer, six to five, though the unrestricted group got larger when the Bucs released or chose not to extend tender offers to seven other players.

The purpose of this annual Free Agency Tracker feature is to keep an eye on all of those players, the men from the Buccaneers' 2009 roster who have new contracts to settle during the 2010 offseason. Some will switch teams - one already has, as you will find below - and some will re-sign in Tampa. The Free Agency Tracker will appear periodically on the site to update all such movement. It is not intended to track players from other teams who sign with the Buccaneers this spring, though any such activity will also be thoroughly covered on Buccaneers.com.

Below are the five players from Tampa Bay's 2009 squad who became unrestricted free agents when their prior contracts expired on March 5. As the free agency period continues and these players either sign with other teams or return to the Buccaneers, the chart will be updated with their developments.

Three Buccaneers also became free agents when they were released just prior to the start of free agency. Though they were not originally slated to become unrestricted free agents this spring, their releases put them in the same category, with the same freedom to negotiate with any team, including the Buccaneers.

Finally, the Bucs essentially increased their list of unrestricted free agents by four more when they chose not to extend tender offers to four players who could have become restricted free agents (more on that category below). Because no offer was extended, these players hit the open market on March 5 like those above, free to sign with any team.

There is a significant difference between restricted and unrestricted free agency. Unrestricted free agents may negotiate and sign with any team, and their previous teams receive no compensation, nor do they have a right of first refusal.

In the 17 previous years of the current free agency system, players became unrestricted free agents when they accrued four seasons of free agency credit and their contracts expired. However, as mentioned above, players must have accrued six seasons before they could become unrestricted free agents in 2010. All players who have three to five years of credit and expiring contracts become restricted free agents as long as their original teams extend a one-year tender offer before the start of free agency.

As was reported Thursday on Buccaneers.com, the Buccaneers extended offers to six of the nine players who were eligible to receive them. Teams have the option to chose from five different levels of tender offers to extend to potential restricted free agents, each of which carries a different one-year salary requirement and a different level of draft-pick compensation should that player sign with another team. All of the offers, however, give the original team the right to match any contract offer the player signs with another team.

The following 2009 Buccaneers became a restricted free agent on February 27 after receiving a tender offer from the team:

Penn and Ruud received tender offers that require another team to send the Buccaneers first and third-round picks in the 2010 draft in order to sign either of them away. Williams' offer returns a first-round pick while Bradley (second), Trueblood (second) and Stovall (third) all received offers that require the return of a pick equal to the round in which they were originally drafted.

Players with expiring contracts and less than three years of credit fall into a third category: exclusive rights free agents. That is what it sounds like - the player's existing team retains exclusive rights to negotiate a new contract as long as they extend the necessary tender offer at the beginning of free agency. Only two players fell into that category for the Buccaneers this year, and they became exclusive rights free agent on March 5 when the team extended the necessary tender offers.

Unrestricted free agents have almost five months to shop their services, as their signing period runs out in July. Restricted free agents have until roughly a week before April's draft court outside offers, after which, if still unsigned, they can negotiate only with their previous team. This deadline allows for time between the signing and the start of the draft, so that any potential draft pick compensation can switch hands before the draft begins.

Only one Buccaneer free agent finalized his home for 2010 over the first weekend of free agency, but that work is just getting started. Check back with the Free Agency Tracker throughout the spring and summer to see where the rest of Tampa Bay's free agents land.