Adam Kaufman of WBZ NewsRadio provided some insight into the move:
Adam Kaufman @AdamMKaufman
Most important factors in #Patriots bringing back Martellus Bennett: Tom Brady trusts him, he’s Rob Gronkowski insurance (if healthy), Dwayne Allen’s been useless, he’s a great blocking tight end, he knows the offense, and - again - Brady trusts him.2017-11-9 21:18:30
The Packers signed Bennett for three years and $21 million in the offseason. At the time, the move seemed like a slam dunk for Green Bay. The team added the veteran tight end it desperately needed, and Bennett was coming off a 2016 campaign in which he caught 55 passes for 701 yards and a career-high seven touchdowns.
However, Bennett was far from a difference-maker in the Green Bay offense. He caught 24 passes for 233 yards and zero touchdowns in his seven games for the team. Football Outsiders ranks him 34th among qualified tight ends in DYAR (defense-adjusted yards above replacement). In comparison, he was third in DYAR at the position in 2016.
During the Packers' bye in Week 8, Bennett even teased retiring from the game altogether:
Bleacher Report @BleacherReport
It appears that @MartysaurusRex will retire at the end of the season per his Instagram Story. https://t.co/tgdzeszxbQ2017-10-28 23:56:44
Still, the fact Green Bay cut Bennett before he was even one full year into his contract surprised many. Rapoport reported the Packers released the 30-year-old for "a failure to disclose designation." Rapoport clarified why that was important:
Ian Rapoport @RapSheet
The #Packers paid TE Martellus Bennett $8M of his 3-year, $21M contract. The only tangible benefit to cutting him with the failure to disclose is if they argue his entire contract is void & go after his money. This isn’t over just yet.2017-11-8 22:21:00
Bennett battled a shoulder injury that forced him to miss Green Bay's Week 9 defeat to the Detroit Lions. The injury would've ruled him out for the team's Week 10 matchup with the Chicago Bears if he had remained on the team long enough.
Between his shoulder injury, lack of production and a possible eye toward retirement, some may question whether Bennett can make an impact for the Patriots in the middle of the season.
But the 10-year veteran is only a season removed from helping the Patriots win a Super Bowl and being among the NFL's best tight ends. Pro Football Talk also posited Aaron Rodgers' broken collarbone sapped Bennett's motivation:
Simplest explanation: Once Aaron Rodgers was injured, Martellus Bennett no longer wanted to be in Green Bay.2017-11-8 22:41:39
When Bennett signed with the Packers, the team had Super Bowl aspirations in 2017. Rodgers' injury changed all of that, as Green Bay became a middling team fighting just to make the playoffs.
Signing with New England, which is much closer to title contention, could lead to Bennett rediscovering his focus.
Given the way his brief tenure with the Packers unfolded, adding Bennett carries slightly more risk that it would've at the start of the season. Still, he could be a big upgrade for the Patriots offense at a critical juncture of the year, which makes this move a no-brainer.