When the Oakland Raiders brought Marshawn Lynch out of retirement ahead of the 2017 season, it was on a two-year contract. With a 32-year-old back on the final year of his contract, they also brought in Doug Martin for the 2018 campaign, and that move proved prescient.

Lynch played only six games before his 2018 campaign was cut short by an injury, so Martin took over lead back duties for the balance of the year.

Not shy about getting the ball to their top back, Martin finished the season having accounted for 45.3% of the team's rush attempts -- the 18th-highest mark in the NFL. Despite the injury, Lynch still just cracked the top 50 with a 21.9% market share. So combined they accounted for 67% of the team's rush attempts, which would have been the league's fourth-highest market share if it belonged to a single player.

Both are set to become unrestricted free agents, and in Lynch's case, there's also the possibility of retirement. That frees up a massive amount of work on the ground.

It also doesn't look like the Raiders have anyone on the roster who will step into that role. Their other top running back, Jalen Richard, was used predominantly in the passing game, with only a 14.1% rushing market share but a 15.6% target market share -- 10th-best among all running backs.

The only other back on the roster to see more than one rush attempt was DeAndre Washington, whose 24 were a career-low, despite the injuries in the backfield.

Richard is also set to become a restricted free agent, but with his significant role in the passing game (and the absolute lack of running backs on the roster), it doesn't seem likely that they would let him walk.

This makes Oakland a prime landing spot for either a free agent or a high draft pick at running back. While spending big on the position might not be the best real-world approach, Oakland's reliance on a workhorse running back even in a 4-12 season is a good sign that Jon Gruden is still high on the position. And that means whoever they add should be in for a ton of opportunity.

Opportunity is the name of the game in fantasy football, especially for running backs. Richard's presence may limit the receiving upside for whoever lands the starting gig, but there should be more than enough rushing volume available to put an addition in the mix as a high-round pick in fantasy football.