It is said that the vice president is just a heartbeat away from assuming the duties of the President. The NFL equivalent is the backup. He’s just one hard hit, or rolled ankle away, from being a starter. It’s the reason fantasy owners must learn to handcuff at important positions.

But just as there is variety in life, so too, there are good backups and bad backups.

Because a player gets an opportunity to play doesn’t necessarily mean he will succeed for his team, or fantasy owners. Some backups are in training to someday take over the starting role while others are just collecting a check until retirement.

Knowing the difference could win you a championship.

Just look at the Philadelphia Eagles quarterback situation in 2013. Michael Vick was the opening day starting quarterback. Early in the season, however, he was injured and backup Nick Foles replaced him in the lineup. Foles was ready to play and went on to a historical season throwing for 27 touchdowns against just two interception in 10 starts. Fantasy owners who handcuffed Foles didn’t lose a beat when Vick went down.

That same season, Josh McCown replaced Jay Cutler in Chicago and went 3-2 in five starts, throwing 11 touchdowns against one interception and earning a 300-yard passing bonus three times.

On the other hand, when fantasy superstar Aaron Rodgers suffered a broken collarbone in Week 8 against the Bears later that year, neither Seneca Wallace (16-for-24 for 139, 0 TDs, 1 INT) nor Scott Tolzien (55-for-90 for 717 yards, 1 TD, 5 INTs) were fantasy-worthy replacements.

The situation isn’t exclusive to quarterbacks.

Last season when Le’Veon Bell was suspended for the first two games of the season, backup DeAngelo Williams produced huge fantasy points for his owners with a 127-yard, 1 TD opener and a three-touchdown second game.

That, of course, was a planned absence. What wasn’t planned was the injury to Cardinals starter Andre Ellington (PCL). First, Chris Johnson took over and played well until he broke his leg, then David Johnson grabbed the football and the rest was fantasy history.

So who will be ready to take over the reins this season?

Let’s look at three quality backups at quarterback, running back and receiver.

Quarterback

1) Brett Hundley, Green Bay

He’s never thrown a regular season pass, but he’d be coming into a very good situation with great receivers and excellent coaches. Just as Rodgers sat and watched a great quarterback in Brett Favre, so too is Hundley watching a great one, and we assume (hope), learning how it’s done. Hundley posted excellent numbers at UCLA (9,966 yards passing, 75 TDs, 25 INTs) and he was 45-for-65 for 630 yards, 7 TDs and 1 INT in the 2015 preseason. He’s a must handcuff for Rodgers owners.

2) Colin Kaepernick, San Francisco

Sure, there are a lot of issues with 49ers’ backup Colin Kaepernick (multiple surgeries, head case), but no one can argue that, when healthy, he has the perfect physical tools for a Chip Kelly offense. He was Marcus Mariota at the University of Nevada before Marcus showed up at Oregon, and in the two years when he took over for Alex Smith in San Francisco from 2012 through 2013 he was an undeniable force. If, and it’s a big if, Kelly can right this ship, it’s possible he could be good once again when Blaine Gabbert inevitably fails.

3) Drew Stanton, Arizona

He’s a veteran with little long-term value, but if Carson Palmer is injured for any length of time in 2016 Stanton has already proven he can get the job done. In 2014 he replaced Palmer for eight starts and went 5-3 with a decent 78.7 QB Rating. With the improved skill position talent on this team in 2016, I’d expect him to be even better.

Talent and offensive scheme make Karlos Williams one of the key RB handcuffs for fantasy owners.