Player signing bonuses are one of the aspects that we take note of when the contract is agreed upon. Given the NFL's collective bargaining agreement, guaranteed money is the figure of note when a player agrees to a deal with a team, and the signing bonus is typically a big chunk of the guaranteed money.
Signing bonuses are often paid in full up front, but teams can also defer payments over multiple dates (the salary cap ramifications remain the same, but the team is able to split up the cash payments to players). This helps the team manage cash flow in terms of managing a yearly budget.
March 31 is a noteworthy date on the NFL calendar for some players, as it is when many of these deferred payments are due.
For the Patriots, a number of players have either deferred signing or option bonuses in their contract to be paid out by tomorrow, highlighted below:
TE Rob Gronkowski: $4 million signing bonus
TE Aaron Hernandez: $3.25 million signing bonus
LB Jerod Mayo: $3 million option bonus
DE Chandler Jones: $2 million signing bonus
OL Logan Mankins: $2 million signing bonus
LB Dont'a Hightower: $1.81 million signing bonus
OL Dan Connolly: $1 million signing bonus
Safety Steve Gregory: $750,000 signing bonus
Safety Tavon Wilson: $707,564 signing bonus
WR Matthew Slater: $700,000 signing bonus
TE Daniel Fells: $300,000 signing bonus
DT Kyle Love: $250,000 signing bonus
Note: Wide receiver Brandon Lloyd had a $1 million deferred signing bonus payment due as well, which he still will receive even though he has been released.