The NFL is a quarterback-driven league. Ever since the modern era of professional football began in 1974 with restrictions on contact with receivers, teams need to pass to score a lot of points. Your quarterback is the face of your franchise, and (apologies to Ravens fans circa 2000), you won’t win much in the playoffs with great defense and a game manager rather than a thrower.

Knowing this, NFL teams overdraft good quarterbacks. I’ve looked into this phenomenon on this blog in the past, and outlined many of the specific cases. In the period I studied, the major overdrafts in recent years were (again, apologies to Ravens fans) Joe Flacco, J.P. Losman, Cade McNown and Joey Harrington. Of those picks, Flacco, drafted 18th in 2008, was justified. The others were not.

This year, the Miami Dolphins are expected to take Ryan Tannehill with the eighth pick. I use Pro Football Weekly to gauge draft interest in players. It uses a consistent evaluation system and front office personnel, in most cases, trust PFW because it protects its sources. Tannehill initially had a draft grade of 5.60 (end of the second round), and has risen (which is unusual, despite all the media attention given to risers) to 6.10 (21st overall) since his recent Pro Day at Texas A&M.

At 5.60, he’d be with Flacco as what would be considered an extraordinary reach at any time in the first round. Obviously, someone in the Ravens organization saw something just about no one else saw. That’s what makes the NFL draft a lot of fun, and one pick like that ensures the reputation of the picker for the rest of his career. No quarterback in the time period I studied (1999-2010) has been drafted in the top 8 with a draft grade below 6.25.

Research showed that overdrafting a quarterback in the first round was a certain losing proposition, until Flacco. The time to take a flier on a prospect was later in the draft. Maybe once in a lifetime you’d get a Tom Brady, or even a Sage Rosenfels.

Until last year.

Maybe it was the Flacco pick that got general managers thinking again. If you can draft a top-half NFL quarterback with the 18th pick, even if he had a high-third-round grade, you’ve changed your franchise. So, after decades when Harrington, McNown and Losman were the only exceptions, Cam Newton (5.99, 23rd overall grade) went to the Carolina Panthers with the first overall pick. Jake Locker (5.77) went 8th to the Titans. Christian Ponder (5.50) went 12th. Andy Dalton and Colin Kaepernick, who had third-round grades of 5.47 and 5.51, went high in the second round. All five of those picks were draft history-changers. And two of them paid off immediately. Newton was pretty good right off the bat. Dalton led the Bengals to the playoffs.

Whereas all five were controversial picks (well, by the time Dalton went, the controversy was long over) in 2011, it’s going to be the norm moving forward. The NFL has always been a trendy league, and with three teams (Baltimore, Cincinnati and Carolina) all receiving dividends from overdrafting a quarterback with an early pick, others will follow suit.

Robert Griffin and Andrew Luck are not in this discussion, as an aside. Both have scouted grades that demand a top-two selection. Luck (8.50) has the highest grade of any quarterback going back to Peyton Manning.

Miami will not be criticized for drafting Tannehill. Nor will any team that looks at the measurables of Kirk Cousins and decides he should go in the second half of the first round. History indicates, however, that both players are long shots.