National League Football teams can't start grocery shopping until March 10.

That's when the 32 clubs can restock their rosters in free agency. The month-long wait might be hard for fans to swallow now that the NFL offseason is in its first week, but that doesn't mean you can't educate yourself on possible roster additions.

The San Francisco 49ers have several notable contributors headed for free agency. The group includes workhorse running back Frank Gore, pass-catching target Michael Crabtree, Pro Bowl left guard Mike Iupati, as well as starting cornerbacks Perrish Cox and Chris Culliver.

The 49ers are permitted to contact, and enter into contract negotiations with the agents of unrestricted free agents on March 7, but contracts can't be executed with new clubs until 1 p.m. PT on March 10.

Prior to 1 p.m. PT on March 10, all 32 teams must:

*-Exercise options for 2015 on all players who have option clauses in their 2014 contracts. *

-Submit qualifying offers to their restricted free agents with expiring contracts and to whom they desire to retain a right of first refusal/compensation.

-Submit a minimum salary tender to retain exclusive negotiating rights to their players with expiring 2014 contracts and who have fewer than three accrued seasons of free agency credit.

-Be under the 2015 salary cap prior to 1 p.m. PT.

Oh, and trades can start being discussed in that same time frame.

As for being educated on the top free agents set to hit the open market, NFL.com's "Around the NFL" crew has shared a list of their top 25 free agents of 2015.

Iupati is the only 49ers representative in the group.

"I really want to stay here, and I'm sure we'll try to work something out," Iupati said at the conclusion of his fifth season in San Francisco.

Do you agree with NFL.com's free agent rankings? Take a look for yourself and share your thoughts in the comments section of this post. 1. Ndamukong Suh, Detroit Lions defensive tackle
2. Justin Houston, Kansas City Chiefs pass rusher
3. Dez Bryant, Dallas Cowboys wide receiver
4. Demaryius Thomas, Denver Broncos wide receiver
5. Jason Pierre-Paul, New York Giants defensive end
6. Julius Thomas, Denver Broncos tight end
7. Mike Iupati, San Francisco 49ers guard
8. Randall Cobb, Green Bay Packers wide receiver
9. Devin McCourty, New England Patriots safety
10. DeMarco Murray, Dallas Cowboys running back
11. Jerry Hughes, Buffalo Bills pass rusher
12. Jason Worilds, Pittsburgh Steelers pass rusher
13. Jared Odrick, Miami Dolphins defensive tackle
14. Pernell McPhee, Baltimore Ravens pass rusher
15. Terrance Knighton, Denver Broncos defensive tackle
16. Jeremy Maclin, Philadelphia Eagles wide receiver
17. Brandon Graham, Philadelphia Eagles pass rusher
18. Torrey Smith, Baltimore Ravens wide receiver
19. Greg Hardy, Carolina Panthers pass rusher*
20. Byron Maxwell, Seattle Seahawks cornerback
21. C.J. Spiller, Buffalo Bills running back
22. Nick Fairley, Detroit Lions defensive tackle
23. Brandon Flowers, San Diego Chargers cornerback
24. Brian Orakpo, Washington Redskins pass rusher
25. Jordan Cameron, Cleveland Browns tight end

*Hardy currently is on the Commissioner's Exempt List