If you managed to stay awake in school when teachers talked about economics, you might remember the term ''opportunity cost.'' Put simply, it describes what you could've bought had you chosen to spend your money differently.

Consider Rob Gronkowski the touchdown-scoring embodiment of that in fantasy football.

The New England Patriots star is the rare tight end worthy of first-round draft consideration. He's the top target in a good offense. And drafting him means securing a mammoth positional advantage that could carry your team right into the playoffs.

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The dilemma: Picking Gronkowski could mean missing out on top running backs like Matt Forte or DeMarco Murray. Or elite receivers like Antonio Brown and Dez Bryant. And that trade-off could put you behind at other critical lineup spots.

It's a big question for teams picking in the back half of the first round: to Gronk or not to Gronk?

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THE REWARD

Look at the 2011 and 2014 seasons for Gronkowski's lineup-carrying potential: he had 90 catches for 1,327 yards and 17 touchdowns in his breakthrough second season, then 82 catches for 1,124 yards and 12 scores last year in his return from a serious knee injury. He's also scored an absurdly good 54 touchdowns in 65 career regular-season games.

Those are elite wideout numbers from a position with far fewer playmakers. And the gap between Gronk and the rest of the field is proof. Consider:

- Gronk scored 184.4 points in standard leagues in 2014 despite missing one game.

- No. 2 scorer Antonio Gates was 30 points behind.

- No. 3 Jimmy Graham - who's had his own mega-star years - was roughly 40 points back.

- And No. 4 scorer Greg Olsen was almost 50 points in the rear-view mirror.

That's a heck of an edge in head-to-head weekly matchups.

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THE RISK

The only thing that has stopped Gronkowski has been injuries. He missed 14 games in 2012 and 2013, though it's fair to point out that injuries can happen to anyone. There's also still the unresolved squabble over quarterback Tom Brady's suspension that could affect his start to the season.

More importantly, who are you giving up to grab him? Want to pass on upside running backs like C.J. Anderson and Jeremy Hill for him late in the first round? Prepare to feel the burn in your backfield.

Here's an example: my longest-running 10-team league held its draft last week. The guy picking last loved Gronkowski's guaranteed production and wasn't sold on the remaining running backs. So he went with two stars: Bryant at 10 and Gronkowski at 11.

When his third-round pick rolled around, the running back options had fallen to players including Joseph Randle, Latavius Murray, Carlos Hyde and T.J. Yeldon - players equal parts potential and uncertainty. He ended up with a backfield of Randle, Doug Martin, Ryan Mathews, Tevin Coleman, Reggie Bush and Cameron Artis-Payne.

The pickings are even slimmer in 12- and 14-team leagues.

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ONE OPINION: It's hard to overlook Gronkowski's position-dominating potential after the top-tier running backs have disappeared. But the drop-off at running back gets ugly fast, and that's probably the determining factor in when to grab him.

If guys like Anderson, Forte, Hill and Murray are still on the board, grab one of them with the goal of snagging a tight end like Olsen or Travis Kelce later in the draft.

If those backs are gone, you're probably in position to grab Gronkowski and maybe a next-tier-down running back (LeSean McCoy, perhaps?) or a receiver from a crowd of top-tier options (Brown, Bryant or Demaryius Thomas).

And if somehow Gronkowski falls to you early in the second, don't hesitate: grab him and run.

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Aaron Beard is an Associated Press sports writer based in Raleigh, North Carolina. He's entering his 14th season of obsessing over lineup decisions in fantasy football. Follow him on Twitter at http://www.twitter.com/aaronbeardap