Big upgrades for Giants, Patriots

The Patriots locked up Darrelle Revis, PFF's top-ranked corner in each of his last two healthy seasons. Michael Thomas/Getty Images

The NFL's new calendar year brings with it opportunity for quick fixes via free agency. Teams look to land veteran help in an effort to plug holes and round out a unit, or even play a part in a major overhaul. A month into that process we can see which teams have made the biggest strides and which of their position groups have benefitted most, using the help of Pro Football Focus' player grades from 2013 (listed in parentheses next to each player; for a description of PFF's grading system, click here).

Here are five units that have seen their stocks rise the most thanks to added free-agent parts.

New York Giants: Offensive line

Players lost: David Diehl (-26.5), Kevin Boothe (-11.3), David Bass (-0.4), Jim Cordle (-5.4)
Players added: Geoff Schwartz (+18.6), J.D. Walton (+5.1, 2012), John Jerry (-2.9), Charles Brown (-9.2)

With problem areas all across the O-line, the Giants came into the free-agency period committed to an overhaul. Diehl retired, Baas was released, Boothe moved on to sign with Oakland and the team didn't tender RFA Cordle, leaving him as an unrestricted free agent. 32-year-old guard Chris Snee missed most of 2013 with a hip injury and took a pay cut to stick around another year rather than retiring, leaving tackles Will Beatty and rookie bright spot Justin Pugh as the only sure starters.