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Darron Cummings/Associated Press

Major changes to the mock draft should surprise long-time readers as quarterbacks, offensive tackles and defensive linemen dominate the top 20 selections. And we didn't leave you out Bears, Browns and Cowboys fans—this mock draft goes three rounds deep.

What causes the big shift in this edition of the mock draft? Free agency.

Teams went into the legal tampering period and started spending money like crazy. The Jets signed Le'Veon Bell and C.J. Mosley, adding clarity to the team's possible direction at No. 3 overall. The 49ers brought in Kwon Alexander and Dee Ford, but could still go with the best defensive player available at No. 2.

Throughout the draft order, team needs were heavily affected by free agents gained, lost or recruited. That means a mock draft unlike anything you've seen under my byline all year long.