The value of a handcuff goes hand-in-hand with the most frustrating and unpredictable dynamics of fantasy football: injuries and snap counts. Determining a handcuff's value is all about assessing whether it's worth using a roster spot on a player who might never sniff value over the course of a full season, simply to hedge a bet on a starting running backs' value.

Because of this, there won't ever be much more than 10 or so handcuff backs worth holding in typical league formats. So, who are those must-own backup running backs? Let's rank the top 5. The criteria: chance to take the starting job, potential production if starting, and bonus points for any value they might hold even as the backup.

DISCLAIMER: Running backs on teams with a murky starting RB situation will not be included, since that takes away the spirit and nature of a handcuff. Nor will Kareem Hunt (already fantasy relevant regardless of situation).

Top Fantasy Football Handcuffs at Running Back

5. Alexander Mattison – Minnesota Vikings

Because he backs up the oft-hobbled Dalvin Cook and brings elite talent when he's on the field (4.6 career yards per carry, 9 career yards per reception), Mattison is one of the most exciting handcuffs to own because of his upside, and his value is even greater given that he's backing up the No. 2 running back in the league (by ADP) in Cook. He showed off his immense upside in his Week 17 start last season, as he posted 145 scrimmage yards and 2 TDs to the tune of 29.5 fantasy points – truly a worthy replacement for Cook. Cook has been able to stay relatively healthy the past few seasons, which is a problem, but Mattison's potential to immediately gain bonafide RB1 status buoys his value.

4. A.J. Dillon – Green Bay Packers

A.J. Dillon is in a similar situation to Mattison, as he doesn't have a realistic chance to supplant Aaron Jones as the lead back in Green Bay on talent alone. However, he would easily offer RB2 value if Jones were to go down with an injury, and he offers some potential as a flex play on his own. Though Jones is the lead back, Matt LeFleur loves to employ a thunder-and-lightning approach with his backs, as we saw last year with Jamaal Williams. Dillon will be taking those reps this year, and, just as we saw Williams offer flex value even when Aaron Jones was healthy, the arguably more talented “Quadzilla” could be even better.

3. Javonte Williams – Denver Broncos

Javonte Williams is currently behind Melvin Gordon on the Broncos' depth chart, but we should expect him to start the year at least as a third-down back. As a monster in pass protection and beast running downhill, Williams could easily provide RB3/low-end flex value to begin the year. Of course, investing a mid-round pick on the rookie is a bet on his upside and will require patience, Williams is probably the only rookie back who begins the year as a clear backup, but could easily find himself in the starting job without an injury to the current starter. He doesn't have breakaway speed, but it wouldn't shock anyone if he's putting up RB2 numbers by the fantasy playoffs.

2. Kenyan Drake – Las Vegas Raiders

Similarly to Kareem Hunt, Kenyan Drake has the potential to supply starting RB value even if he's the clear backup behind Josh Jacobs in Las Vegas. However, we simply don't know if that'll happen since this will be Drake's first campaign in the silver and black, and because he simply didn't live up to expectations as a starter with the Arizona Cardinals. If any injury were to occur to Josh Jacobs, though, Drake would become an easy RB1 based on volume alone. The Raiders run the ball a ton, and Jon Gruden has shown that he loves a workhorse runner for the early downs. It's a risky proposition, but holding onto Drake could eventually pay big dividends.

Honorable Mentions

Gus Edwards – Baltimore Ravens, Darrel Williams – Kansas City Chiefs, James Conner – Arizona Cardinals, Rashaad Penny – Seattle Seahawks, Tony Pollard – Dallas Cowboys, Latavius Murray – New Orleans Saints.

1. Trey Sermon-  San Francisco 49ers

Trey Sermon seriously has the potential for a huge 2021 and to be the best of these fantasy football handcuffs. Not only does he back up Raheem Mostert, one of the most oft-injured players in the league, but he possesses the talent to charge RB1 value into fantasy lineups if given a feature role as well. As a big back at 215 pounds, paired with graceful agility and balance to evade and break tackles, Sermon is a perfect fit for the 49ers zone run scheme. He also has great hands, giving him a true three-down skillset, and, though Kyle Shanahan often applies somewhat of a committee approach to his backfields, we have seen the hot hand dominate at times as well. Any injury to Mostert or breakout from Sermon should vault him into RB2 territory, at minimum.