Dating back to 1950, it would be the first time that four rookie quarterbacks start their team's first game, according to STATS LLC.
"Quarterbacks are learning earlier, learning faster and they've gotten so much better over the years," NFL.com senior analyst Gil Brandt said.
"I think it is really fortunate that we get to put the piece in place now and build around the franchise quarterback," Irsay said.
The Redskins gave up three first-round picks and a second-rounder to have Heisman Trophy-winning Griffin replace the wildly inconsistent Rex Grossman.
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Brandt called Tannehill the "real deal."
"He's everything you want. Smart, accurate, has speed, and good feet," Brandt added. "The only knock on him is that he hasn't played a lot. But here's how good he is: He is the only quarterback to beat Oklahoma, Nebraska and Texas in the same year, and did it over a six-game span."
"I wasn't concerned about his age," Browns coach Pat Shurmur said of Weeden, who spent five years in baseball's minor leagues before returning to football. "I was impressed with his maturity and production on tape. We became very fond of him."
Copyright 2012 by The Associated Press