Jim Corbett

USA TODAY Sports

Let the spending frenzy commence.

After days of anticipation filled with seemingly spontaneous franchise tags and new deals for current roster players, 4 p.m. ET marks the start of free agency's open season.

NFL teams can pursue opposing players hoping to lure them with fists full of cash. The ultimate goal for NFL teams is to fill needs to help them better focus on other areas of need in May's NFL draft.

So here are five things you should know entering free agency:

Biggest fish available

Beyond the big four tackles (Eugene Monroe, Branden Albert, Rodger Saffold, Jared Veldheer), who are likely to attract big paydays, Cincinnati Bengals defensive end Michael Johnson will command an early mega deal. Michael Bennett helped the Seattle Seahawks capture their first-ever Lombardi Trophy playing on a one-year, $4.8 million deal before re-signing Monday afternoon for four years worth $28.5-million. Bennett has more name recognition, but the 6-7, 260 Johnson, 27, is one year younger, can play right defensive end or stand up and is more complete against the run. With 26 ½ career sacks, Johnson also has three more career sacks than Bennett. Expect the Tampa Bay Buccaneers, Chicago Bears and Atlanta Falcons to be among the suitors vying for Johnson.

Plenty to spend

The salary cap increase by $10 million per team to a record $133 million should make these six teams early players in free agency:

* Oakland Raiders general manager Reggie McKenzie is ready to shop given a league-best $55.8 million to spend, according to NFLPA salary data obtained by USA TODAY Sports.

* The Miami Dolphins have plenty in available salary-cap room with $33.6 million.

The Jonathan Martin-Richie Incognito bullying scandal has left the Dolphins offensive line decimated facing a total rebuild on the left side where left tackle Martin and guard Incognito must be replaced.

* The Jacksonville Jaguars ($46.9 million), Cleveland Browns ($42.9), and Indianapolis Colts with $34.4 are among NFL's top teams in terms of available cap space. And the Bucs figure to be major players with $23.65 million as new coach Lovie Smith finds fits for his Cover 2 scheme.

Diamonds in the rough

* Start with Kansas City Chiefs guard Jon Asamoah, a starter at right guard since 2011, who lost his job to Geoff Schwartz after a November shoulder injury. Asamoah is a good pass protector, and the Atlanta Falcons desperately need to better protection for quarterback Matt Ryan. Asamoah was drafted in 2010 by former Chiefs general manager Scott Pioli, now the Falcons' assistant GM. Figure the New York Jets also to have interest.

* Carolina Panthers safety Mike Mitchell surrendered just one touchdown last season and brought playmaking and swagger to the Panthers secondary with 66 tackles, four interceptions and 3 ½ sacks. He is not the ball hawk Jairus Byrd is, but he'll be cheaper for teams like the Philadelphia Eagles, Washington Redskins, Denver Broncos and Falcons.

Teams likely to become weaker

* The New England Patriots would be undercut if a team swoops in and signs cornerback Aqib Talib, Bill Belichick's best cover corner.

* The cap-strapped New Orleans Saints could lose tackle Zach Strief, center Brian De La Puente and safety Malcolm Jenkins.

* The Panthers could lose two young starters in Mitchell and receiver Ted Ginn, who were integral to a 12-win season.

Remember last year?

* Former Pittsburgh Steelers speed receiver Mike Wallace landed a market-best, five-year, $60-million deal only to give the Dolphins a career-low five-touchdown, 930-yard return.

* The Seahawks sat out the opening of free agency, then struck below-market deals with defensive ends Bennett and Cliff Avril, who received $13 million over two years.

Their Super Bowl payoff? Priceless.