The Green Bay Packers may be down to just four active receivers when they take on the Jacksonville Jaguars Sunday at Lambeau Field.

Greg Jennings is already out for Sunday, and the two-time Pro Bowl receiver revealed the new plan for dealing with his lingering groin injury Thursday. Jennings, who has missed the better part of five games this season, said that he will undergo surgery on his groin next Tuesday. His timetable is not a season-ending one, but Jennings wasn't willing to give anything concrete Thursday.

Jennings isn't the only concern at receiver.

Leading receiver Jordy Nelson, who missed Thursday's practice with a hamstring injury, also won't practice Friday and is now in doubt to play Sunday.

According to Packers head coach Mike McCarthy, Nelson's hamstring "tightened" up during Wednesday's practice, but it appears the injury is more significant than just a slight tightening of the muscle. Nelson may test the hamstring Saturday or Sunday, but he'll likely be listed as questionable to even doubtful for Sunday game.

If Nelson can't go, the Packers would be down to just James Jones, Randall Cobb, Donald Driver and Jarrett Boykin at the receiver position.

While Jones (29 receptions, 323 yards, seven TDs) and Cobb (37, 435, three) have been productive in 2012 and are starting-caliber players, Driver and Boykin have not been on the field for many snaps. Driver (four, 45, one) and Boykin (0,0,0) have played a combined 88 snaps over seven games this season.

Driver, who sat out Wednesday's practice with a neck issue, returned Thursday. The 37-year-old could receive his highest snap total of the 2012 season Sunday.

McCarthy was also confident in Boykin being able to contribute.

"He'll play, and he'll do the same things that are asked of the other guys," said McCarthy, who complimented the way Boykin has picked up the offense. "He knows all four positions."

Rodgers on free plays

According to ESPN NFC North blogger Kevin Seifert, no quarterback in the NFL has awarded himself more "free plays" since 2011 than Aaron Rodgers.

A "free play" is considered one where an official throws a penalty flag for defensive encroachment, likely because of the quarterback's cadence, but the play goes on after the snap. At that point, a quarterback can really attempt anything it wants with little to no risk.

Seifert, citing numbers from ESPN Stats and Information, wrote that Rodgers has attempted an NFL-high 14 post-encroachment passes over the last two seasons. He completed five of the 14 for 128 yards, two touchdowns and two interceptions, with the average pass traveling over 25 yards in the air. Two such passes—a 52-yarder to Nelson and 39-yard touchdown to Cobb—came last Sunday in St. Louis.

The numbers come as no surprise. Rodgers has mastered the art of cadence, and he's aware enough to take the risk-less shots down the field on free plays. Sometimes he hits, sometimes he doesn't. But taking the risk is always the right call, and Seifert's numbers confirm that Rodgers has done exactly that.

Playaction numbers drop

Interesting numbers coming from Pro Football Focus Thursday.

The football analytics site now tracks playaction passing, and the numbers do not look good on the surface for Rodgers and the Packers.

According to PFF's new signature stat, no quarterback's completion percentage drops more (17.0 percent) than Rodgers when using playaction (55.3 percent) this season. In comparison, Rodgers completes 72.3 percent of his passes when not using playaction.

The rest of Rodgers' numbers when using playaction: 44 dropbacks, 21-of-38 for 294 yards, three touchdowns and two interceptions. His passer rating is 84.5 and yards per attempt 7.5.

No playaction? Here's those numbers: 258 dropbacks, 162-of-224 for 1,685 yards, 16 touchdowns and two interceptions. His passer rating is 113.8 (best in NFL by 13.8 points) and yards per attempt 7.5.

What could cause this significant gap?

For starters, the Packers have not had a run game that strikes the necessary fear into opposing linebackers and safeties. At its very core, playaction is designed to get linebackers and safeties moving forward at the snap to open up receivers and passing lanes that wouldn't normall occur without it.

But digging deeper, the Packers probably take more risky shots downfield off playaction than most NFL teams. How many times this season has Rodgers used playaction on 3rd-and-short and just missed a receiver downfield? Generally, the higher the risk of a throw, the lower the percentage. That applies here for Rodgers when McCarthy dials up a playaction pass.

Combining the two factors—defenses not fearing the Packers run game and the higher risk of calls off playaction—are probably to blame for Rodgers' remarkable dropoff in accuracy.

Zach Kruse is a 24-year-old sports writer who contributes to Cheesehead TV, Bleacher Report and the Milwaukee Journal Sentinel. He also covers prep sports for the Dunn Co. News. You can reach him on Twitter @zachkruse2 or by email at [email protected].