Jerry Jones and DeMarcus Ware have talked a lot this offseason about the Dallas Cowboys' window of opportunity.

Father Time hasn't caught up to the Cowboys, but he's nipping at their cleats. Ware turns 30 on July 31, which will put the core group of Ware, quarterback Tony Romo, tight end Jason Witten and defensive tackle Jay Ratliff in its early 30s. Once that group ages, the Cowboys will be forced to rebuild.

But a new problem, which has little to do with age, faces many franchises. Projections of flat salary caps will force more teams to pick and choose which of their core players can stay and which will go. That process started this offseason, when the Houston Texans said goodbye to defensive tackle Mario Williams and offensive tackle Eric Winston and the New Orleans Saints decided they couldn't keep together the league's best guard tandem of Jahri Evans and Carl Nicks. Nicks was let go and signed with the division rival Tampa Bay Buccaneers.

An average of 10 starters per team will become free agents in the next two offseasons. If the salary cap goes up only $1.4 million to $2 million per team over the next two years, general managers and coaches will agonize over which players they can keep.

Studying the list of starters who will be free agents is stunning. The Cowboys' window might be closing, but other franchises might find their windows of opportunity shut before they know it.

Here are teams that face tough decisions in 2013 and 2014:

1. Chicago Bears: Of the Bears' 22 projected starters, 17 have contracts that expire by 2014. Only defensive end Julius Peppers, linebacker Lance Briggs, receiver Brandon Marshall, offensive tackle Gabe Carimi and safety Chris Conte are under contract through the 2015 season. QB Jay Cutler has two more years on his contract, so the Bears must make every effort to win in 2013 and 2014 or they might have to break up the team. It explains why the Bears can't go overboard in giving a long-term deal to running back Matt Forte. Chicago has about $13 million of cap room in 2013 and more than $50 million of cap room in 2014, so it can handle an important re-signing such as Cutler. But big decisions must be made on defense because linebacker Brian Urlacher, who turned 34 in May, will become a free agent after this season and cornerback Charles Tillman will become a free agent after 2013.

2. Detroit Lions: General manager Martin Mayhew has built a powerhouse offense of skill players around quarterback Matthew Stafford, and that group will be around for years. By the end of 2013, though, four-fifths of the Lions' projected starting offensive line will hit the market. The bigger issue is defense. After going 0-16 in 2008, the Lions sacked their entire starting defense. They've done a nice job rebuilding the defensive line, but the bill will come due for what they've done at linebacker and in the secondary. Five starters at linebacker or in the secondary are free agents after this coming season, including linebacker DeAndre Levy and safety Louis Delmas. With the Lions already over next year's cap, they must be selective on which starters stay.

3. New York Jets: Eight starters will be free agents after this season, with the biggest decisions coming on offense. If Shonn Greene proves to be the workhorse running back the organization believes he can be, he might be too costly to keep. He's a free agent in 2013. So is tight end Dustin Keller, who might get a franchise tag. Overall, a dozen starters could be free agents over the next two years, including cornerback Darrelle Revis. If the Jets don't do anything with Revis' contract this season, they must do something next year. He's a free agent after 2013, and the team has waived its ability to franchise or transition him. The Jets are already more than $19 million over next year's cap, making things even tougher.

4. Oakland Raiders: New general manager Reggie McKenzie, who had to wade through serious cap issues in 2012, will closely eye this season's starters. The Raiders have cap room next year and a lot of room in 2014. Still, 10 projected starters will be free agents at the end of this season, and five more will be free agents after 2013. On defense, tackle Richard Seymour, safety Tyvon Branch, cornerback Ron Bartell and cornerback Shawntae Spencer are among the players who will be free agents at the end of this season. Decisions on the offense come after the 2013 season. Running back Darren McFadden, receivers Darrius Heyward-Bey and Jacoby Ford and offensive tackle Jared Veldheer are free agents after the 2013 season.

A playoff run this season may affect how the Chiefs deal with Dwayne Bowe and others whose contracts expire soon. Otto Greule Jr/Getty Images

5. Kansas City Chiefs: A playoff run would do a lot to persuade general manager Scott Pioli to spend plenty to keep this team together. A bad season might force change. Offensive tackle Branden Albert, franchise wide receiver Dwayne Bowe, guard Ryan Lilja and defensive end Glenn Dorsey are in the final year of their contracts. Defensive end Tyson Jackson, tight end Tony Moeaki and safety Kendrick Lewis will enter the final year of their contracts next season.

These teams are geared to make big runs over the next two seasons:

1. Philadelphia Eagles: Coach Andy Reid has 21 of his 22 projected starters under contract through 2013, and 18 are signed through 2014. A bad season, though, could force change. The Eagles are more than $16 million over next year's cap. If the Eagles are not a "dream team" this season, many of their veterans could have sleepless nights in the offseason.

2. San Francisco 49ers: Coach Jim Harbaugh brought back all 11 offensive starters from last season's team. In fact, all 11 projected starters on offense are signed through 2013, so the 49ers are geared for at least a two-year run. Franchise safety Dashon Goldson and nose tackle Isaac Sopoaga are the only starters who will be free agents after this season. Seven projected starters come free after 2014.