If Calvin Johnson retires, the Lions have even more cap flexibility

Calvin Johnson is moving closer and closer to retirement, which means the Detroit Lions will potentially have another $11.1 million to work with in free agency.

Receiver is going to become a much bigger need for Detroit, either through a fairly weak free agent class or a pretty strong draft class. There are other ways the Lions could use the extra money they'll have – on top of the potentially $20 million in cap money available.

Johnson's retirement might make the Lions more willing to keep some of the players under contract that are potential cap casualties: linebacker Stephen Tulloch, running back Joique Bell and tight end Brandon Pettigrew.

Tulloch is costing the Lions the most among the three in 2016 at $7.3 million. Pettigrew has a $4.65 million hit and Bell a $3.5 million charge. So one ---- or maybe more -- of the three could end up sticking with Detroit because of the extra money to work with.

Beyond that, the Lions have many holes they have to fill through either the draft or free agency other than receiver.

The offensive and defensive lines are the biggest need areas for Detroit. Offensive tackle is a place where the Lions have to try and find an upgrade and there are strong potential free agent options on the market.

There are strong potential free agent options, particularly with Seattle's Russell Okung and Buffalo's Cordy Glenn. Okung could end up being available, but Glenn could be a franchise tag candidate for the Bills. If the Lions were able to sign either one, that would give them flexibility on Riley Reiff, who has been Detroit's left tackle the last three seasons.

Defensive tackle, which is the bigger need than end for the Lions, is a tougher spot to find elite talent in free agency. But if Detroit wanted to try and invest in an end opposite Ezekiel Ansah, Miami's Olivier Vernon could be an option.

Vernon has been reliable -- he's played in every game during his four-year career, has 29 career sacks and at age 25 still has a lot of years in front of him.

There are some other good defensive line options for Detroit as well. Muhammad Wilkerson from the Jets is a top-flight option and could give the Lions stability in the middle of the defensive line. Like many other top-end players who are heading toward free agency, the Jets could use the franchise tag on him. If they don't, he could give Detroit the interior presence it had when Ndamukong Suh was with the Lions.

The 26-year-old Wilkerson has played in 77 games with 302 tackles with 36.5 sacks.

If Akiem Hicks reaches free agency, the 26-year-old is someone general manager Bob Quinn is familiar with since he was in New England this season (21 tackles, three sacks).

Safety is also an area where the Lions could choose to spend -- especially with James Ihedigbo and Isa Abdul-Quddus heading toward free agency.

San Diego's Eric Weddle is expected to reach the market and could be a Lions target. His age, he turned 31 in January, is a likely issue but he's consistently been one of the better strong safeties in the league. Plus, he already has a relationship with Lions free safety Glover Quin as the two were texting during the 2015 NFL schedule release last year.

Kansas City's Eric Berry, who has been one of the best stories in the NFL this season coming back from cancer, is also scheduled to be a free agent. It would be surprising to see him hit the market considering his recovery and his age (he's 27), but if he's out there, the Lions would have money to spend.