Malik Jackson had a nice opening day.

The defensive end had four teams who expressed serious interest in obtaining his services: The Jacksonville Jaguars, John Fox’s Chicago Bears, John Elway’s Denver Broncos and Jack Del Rio’s Oakland Raiders.

The free-agent tampering window opened at 11 a.m. Monday. During this period, opposing teams can work out contract details with potential free agents but an agreement cannot be executed with signatures until the market opens at 2 p.m. Wednesday.

Jackson played the past four seasons with the Broncos and his coming off a breakout year in 2015 when he compiled 21 quarterback hurries, 16 quarterback hits, seven pass deflections (second among NFL defensive linemen to J.J. Watt’s eight) and 5.5 sacks.

Jacksonville has the league’s most salary cap space at $82.2 million. Oakland is third with $60 million in cap space, the Bears are seventh with $46.5 million and the Broncos are 30th with $9.05 million.

However, the Broncos are not out of the Malik sweepstakes because the team just received $19 million in cash savings from Peyton Manning’s retirement and the team is trying to finalize salary reductions for outside linebacker DeMarcus Ware and left tackle Ryan Clady.