New England Patriots tight end Rob Gronkowski missed his sixth straight game of the season on Sunday.  Amidst the uncertainty of his return, money may be a factor that causes Gronkowski to sit the entire season.  Teammates, meanwhile, are reportedly becoming resentful about the situation.

Gronkowski, who's recovering from four left arm surgeries and one back surgery, has been a full participant at practices but has yet to play in games.  New England has said the decision when to return is entirely up to Gronkowski.  At just 24 years old, Gronkowski and his camp want to be cautious with his return; he is reportedly waiting to be cleared to return by Dr. James Andrews, a doctor outside the Patriots medical staff.

A report from the Boston Globe, however, suggested money may also be a strong factor in Gronkowski's decision to return - strong enough that it could make him choose to sit for the entire season. 

"Gronkowski signed a contract extension in 2012 worth a maximum of $55 million, but he needs to stay healthy all the way through the 2015 season to receive most of it - which, after the medical scares of the last 12 months, looks like a daunting task," Ben Volin of The Globe wrote on Monday.

Gronkowski is set to make just $630,000 this season.  He makes base salaries of $3.75 million in 2014 and $4.75 million in 2015.  If he can remain healthy through the 2015 season, he's eligible for a $10 million bonus, which The Globe suggested may be an incentive for him to miss the season.

Although the team has publically supported the Pro Bowl tight end, there's reportedly friction between Gronkowski and the Patriots staff.  The alleged rift, according to ESPN, is now spreading to the locker room.

"There's curiosity and resentment, and he's creating it by going out and kicking ass during the week and then he doesn't show up on game day and help the team win," a source told ESPN.  "... If he's not playing in games, he damn sure should not be doing what he is in practice."

Sources added that teammates have begun to openly show their frustration to Gronkowski, making it an "uncomfortable" situation for him in the locker room.  ESPN's sources also said some players are wondering if Gronkowski is even planning to play this season.

Gronkowski, per Pro Football Talk, is expected to miss "at most" one more game.  The Patriots travel to New York on Sunday to play the Jets.