How good do rookie QBs need to be?

Newly selected first-round draft choices Blake Bortles, Johnny Manziel and Teddy Bridgewater have been mentioned as candidates to sit and watch at the start of the 2014 season, and their new teams have made the usual comments about not wanting to rush their young prospects onto the field. Moreover, nearly every evaluator I've encountered thinks the 2014 quarterbacks aren't ready to play at as high a level as rookie stars Andrew Luck, Robert Griffin III, Russell Wilson and Matt Ryan did just yet.

But here's an important stat to remember amid that discussion: 14 of the last 16 first-round quarterbacks started more than eight games as rookies, and 10 started at least 14 games. The trend is clear. NFL quarterbacks have made 243 starts as rookies over the past four seasons, up from 131 from 2006 to '09 and 133 from 2002 to '05.

So, while no one knows how much Bortles, Manziel or Bridgewater is going to play in 2014, precedent justifies considering how well their teams might fare with them in the lineup. One of the projects I've worked on this offseason could help along these lines. I started by dividing NFL defenses into performance quartiles, then looking to see which teams play the most games against the best defenses. Some of the disparities uncovered were striking. St. Louis and Cincinnati have big decisions to make about their quarterbacks, but the Rams play a league-high eight games against defenses that finished 2013 ranked in the top quartile, as measured by defensive expected points added, while the Bengals play only one game against a defense in that category.

What do similar dynamics say about how Bortles, Manziel and Bridgewater might fare as rookies? What types of recent performances by other rookies might these three first-round choices need to approximate for their teams to reach the playoffs? The numbers offer some answers.