The Patriots defensive core has come into focus this weekend, and the re-signing of cornerback Aqib Talib is an indication they liked the momentum created late last season. Talib inked a one-year, $5 million contract yesterday, according to two sources, and he joined cornerback Kyle Arrington (four years, $16 million) among players who earned new deals in recent days. Safety Adrian Wilson also joined the club to give the secondary an added bit of nastiness over the middle. But the Talib deal tied the first week of free agency all together, and the contract materialized for a number of reasons. Even though the deal’s parameters weren’t each side’s first choice, it all could work out perfectly when it’s all said and done. First, the market for cornerbacks bottomed out, which played directly into the teams’ hands, particularly a value-conscious Patriots front office. The flattened salary cap led to some additional veteran releases, and there were a couple dozen starting-caliber corners in free agency, led by a solid top tier.