The link between the Giants and the Packers, as far as 
Blake Martinez and 
Kyler Fackrell are concerned, is the Giants brand new defensive coordinator 
Patrick Graham, who is black. Graham played his college football at Yale (defensive end), beginning in the mid-1990's. When Graham played, I  believe Ivy League schools tended to cut mediocre student-athletes  a bit 
less slack  than they have in recent years.
Graham  spent a long time as a position coach with the Patriots, then made his way to Green Bay for one year  in 2018, where coached the linebackers -- Martinez and Fackrell had career years with Graham. He left G.B. for Miami last year, following his friend Brian Flores. With Graham's urging, as defensive coordinator, the Dolphins traded for ex-Packer linebacker 
Vince Biegel, even though he never did anything in Green Bay to warrant that confidence, DWF's might say? But Biegel came through big time for Graham as a starter and was recently awarded with a nice extension by the Dolphins. Having spent time in Wisconsin in 2018, Graham might've also persuaded the Dolphins to draft ex-Badger OLB Andrew Van Ginkel? AVG  played really well in Miami after returning from the I.R.? Hopefully the Dolphins new D.C. is as fair minded as Graham, to AVG and Biegel?
With Graham in the fold, the Giants will utilize a 3-4 base defense. Connelly coming back from injury should be a starter. Mayo played well enough to be a starter last season and Martinez got starters money! Problem is all three are inside linebackers. My guess is, coming off a ACL injury, Connelly and Mayo split one spot, Martinez also  starts, barring injury. Fackrell starts early, but has to stave a pair of  "upsiders" from recent drafts. Giants suddenly have 4 top notch white linebackers on their roster, 
with 3 likely starting. Probably hasn't happened since the 1970's?