In 2014, it was the 27-year old linebacker Jonathan Casillas and 25-year old edge rusher Akeem Ayers.
In 2015, it's 25-year old defensive tackle Akiem Hicks and 24-year old linebacker Jon Bostic.
Don't think for a second that Bill Belichick and Nick Caserio are done- there's still room to improve the roster.
There is a clear strategy for the Patriots approach in player acquisition as they trade for expiring contracts from teams that have given up on the season. Talib, Casillas, Ayers, and Hicks were all in their final contract years.