What does Blay have to do with whether Jacobs makes the team? Blay is a DT. Jacobs is a LB. Blay would have to beat out Taylor, Pharms, and Gregory. Blay's 3-cone and Short Shuttle suck. He's got a decent Bench, but lacks explosion as seen by his 8'9 Broad. From Brugler's Beast, about the only thing Blay's got going for him is his hands and even those are a work in progress.
The Pats carried 5 DTs most of the year and they carried 5 LB once Tavai was healthy. It's highly unlikely that Blay makes the team.
Jacobs, on the other hand, is going against Britt, Muma, Obiazor, Hutchins, Reese, and Gainer. There are 7 guys for 3 spots. Britt, Muma, Reese, and Gainer all have Special Teams experience already. Britt and Muma have some experience taking defensive snaps that should give them the upper hand, but Special Teams will be the decider for all 3 LB positions behind the starters.