Bill Belichick fielded one of the youngest defensive units in the NFL last season, and still made it to the AFC Championship game.

“One year older, one year wiser” should be the defense’s mantra heading into 2013, and to make certain that the players indeed get one year wiser and not just one year older, the leverage junkie has brought in private tutors for his young greyhounds…

Oct 28, 2012; Kansas City, MO, USA; Kansas City Chiefs quarterback Matt Cassel (7) is pressured by Oakland Raiders defensive tackle Tommy Kelly (93) in the second half at Arrowhead Stadium. Oakland won the game 26-16. Mandatory Credit: John Rieger-USA TODAY Sports

So far in free agency, Belichick has signed 12 year veteran safety Adrian Wilson, re-signed 6th year Cornerback Aqib Talib, and on Monday afternoon signed defensive tackle Tommy Kelly, formerly of the Oakland Raiders.

Kelly, in his 9th year as an undrafted free agent out of Mississippi State, was once considered one of the top five tackles in all of the NFL, but playing in different systems and being moved all over the defensive line Oakland limited his stat line. Once he teamed with Richard Seymour as a 3-technique tackle in the Raiders’ 4-3 base alignment, it freed up Kelly to do what he does best: Rush the passer from the interior…

…and that’s what the Patriots will be counting on Kelly for on the field, as a passing situation interior rusher. Off the field, they are counting on him for something that some feel is even more important: Mentoring the younger tackles, “rookie” Armond Armstead in particular.

Reading between the lines, it is clear that Belichick has both filled his need for a situational interior pass rusher as well as seeming to be satisfied that Armstead is everything he thought he was, and is the future at the position. That being said, Patriots’ fans will now probably not see Belichick use one of his meager draft picks totals on a defensive tackle…

…but you can be sure that he’s going to use one on a cornerback. Aqib Talib was resigned for just one season, and the thinking is that as long as Alfonzo Dennard progresses from his solid rookie season at the opposite corner, drafting a corner that can be mentored behind Talib for a full season could bring next offseason more in focus, as the Patriots would have an experienced corner to take over in the event they can not or will not resign Talib, who will be looking for his big payday.

Though Talib doesn’t strike one as the warm and fuzzy mentoring type, former Cardinals’ strong safety Adrian Wilson does, except for that warm and fuzzy talk.

The hard hitting four time first team All Pro understands his role at this point in his career, and that is to mentor 2nd year load Tavon Wilson to be the enforcer that completes the Patriots’ secondary…and it is also possible that the Patriots look for a developmental safety in the draft as well.

Bill Belichick doesn’t just arbitrarily bring in has-beens who contribute a few plays while backing up their truck to the depository at the bank – though at times it seems like just the case – and this year his intentions are very clear: Fill holes with able veterans who will train and turn over their jobs to eventual successors.

And as long as they’re cool with that, the Patriots have accomplished what they set out to do in free agency.