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Lingering Free Agent Quarterback A is a 29-year-old with no Pro Bowls on his resume and the following career numbers: 58 starts, 59.8 percent completion rate, 72 touchdowns, 30 interceptions, 7.3 yards per attempt, 88.9 passer rating. He's also scored 13 rushing touchdowns while averaging 33.3 rushing yards per game. He was a second-round pick six years ago.

Lingering Free Agent Quarterback B is a 27-year-old with a Pro Bowl on his resume and the following career numbers: 40 starts, 63.3 percent completion rate, 42 touchdowns, 26 interceptions, 7.4 yards per attempt, 88.4 passer rating. He's also scored 10 rushing touchdowns while averaging 39.8 rushing yards per game. He was a top-three pick just five years ago.

Everybody is talking about Lingering Free Agent Quarterback A, presumably because his name is Colin Kaepernick and he's become the NFL's unofficial lightning rod.

Nobody is talking about Lingering Free Agent Quarterback B, but it's difficult to pinpoint just why that is. His name is Robert Griffin III, his career numbers are similar to Kaepernick's, they're both known for their mobility and RG3 has the edge when it comes to pedigree and age. He came into the league with more hype than Kaepernick, was the Offensive Rookie of the Year in 2012 and was sunk by injuries and deteriorating performances beyond that.

Robert Griffin III vs. Colin Kaepernick Category Griffin III Kaepernick Age 27 29 Drafted 2nd, 2012 36th, 2011 Seasons 5 6 Starts 40 58 Record 15-25 28-30 Completion % 63.3 59.8 Touchdowns 42 72 Interceptions 26 30 Yards/attempt 7.4 7.3 Passer rating 88.4 88.9 Rush yards/game 39.8 33.3 Rushing TD 10 13 Pro Football Reference

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Griffin hasn't been at his best since that 2012 season and was last relevant when he completed 60.1 percent of his passes for 3,203 yards, 16 touchdowns, 12 picks and posted an 82.2 rating in 13 starts in 2013. His excuse then was that he was coming off reconstructive knee surgery, but he wasn't the same player in 2014 or 2015, taking a back seat to Kirk Cousins in Washington.

Kaepernick is, again, in a similar boat. He was at his best in 2013, when he completed 58.4 percent of his passes for 3,197 yards, 21 touchdowns, eight picks and posted a 91.6 rating in 16 regular-season starts before leading the 49ers to their second consecutive NFC Championship Game appearance. But he averaged just 7.0 yards per attempt and ranked 20th among 33 qualified passers with an 86.4 rating the next year and was benched in 2015. He only earned starts in 2016 because San Francisco had no other options (Blaine Gabbert doesn't count).

By now you've heard the conspiracy theories regarding Kaepernick, who became the league's most polarizing figure with his protests during the national anthem last season. But there's strong evidence the league figured out how to solve Griffin and Kaepernick between 2013 and 2015. Those two were difficult to stop when they took the NFL by storm, but defensive coordinators learned how to slow them down and made adjustments.

When I wrote last month about the dearth of left-handed quarterbacks in today's game, several of the football folks I spoke to posited that teams might favor right-handed quarterbacks for backup jobs if they have righty starters.

"We're probably not going to take you because you're a lefty, we have a righty starter and I think it's hard to have a lefty backup when all of your offense is tailored for the righty starter," left-handed Dallas Cowboys quarterback Kellen Moore recalled being told.

In a similar vein, it's entirely possible that Griffin and Kaepernick aren't on NFL rosters because they're not seen as starters right now, and because teams don't view them as backups who can mimic their more prototypical starters (like, say, Gabbert or Ryan Fitzpatrick). It's also possible teams aren't interested in employing quarterbacks whom they feel they figured out how to neutralize just a couple of years ago.

Don Wright/Associated Press

These are just theories, but the fact that both remain on the market and only one took a knee during the national anthem could indicate there's more to the story. And it's probably not a coincidence that the Seattle Seahawks, the one team that publicly expressed interest in Kaepernick this offseason, also stated interest in Griffin.

So both quarterbacks may need to wait for starting quarterback dominoes to fall (i.e., training camp injuries), and it shouldn't shock anyone if Griffin gains employment before Kaepernick. He was terrible early last season with the Cleveland Browns, but that sample is small and he was returning from a major shoulder injury. He was a No. 2 overall pick and the Offensive Rookie of the Year for a reason, and at 27, he still has plenty of time to redeem himself after several forgettable seasons.

Highest-rated rookie seasons in NFL history Quarterback Team Year Rating 1. Dak Prescott Cowboys 2016 104.9 2. Robert Griffin III Redskins 2012 102.4 3. Marc Bulger Rams 2002 101.5 4. Russell Wilson Seahawks 2012 100.0 5. Ben Roethlisberger Steelers 2004 98.1 Pro Football Reference (min. 200 attempts)

Griffin has lost 19 of his last 25 starts, but this is a team game. And Kaepernick has lost 16 of his last 19.

I covered Griffin closely while on the NFC East beat for Bleacher Report between 2012 and 2014, and watching him as a rookie was truly special. He might no longer possess the mobility he did then, but quarterbacks have long shelf lives in comparison to players at other positions.

His mechanics, his footwork and his mentality need work, and he hasn't been the same since suffering that knee injury at the end of his rookie season. But if he can get even halfway back to where he was five years ago, RG3 could still be a pleasant surprise in 2017.

Brad Gagnon has covered the NFL for Bleacher Report since 2012.

Follow @Brad_Gagnon