Taken 20th overall in the 2008 NFL Draft, Talib is 6'1, 202 lbs, with a 4.44 40 yard dash. He's explosive and quick and has been Tampa's #1 cornerback since early on his career and has historically been given the task of shadowing the opposing team's #1 receiver. According to Pro Football Focus, Talib is rated as one of their top 20 cornerbacks over the past three seasons and was on track to having another solid year.
Unfortunately, Talib has his fair share of issues off the field, which is why the Patriots were able to acquire him for such a reasonable price. Talib got into a fist fight during his rookie camp in 2008, was arrested in 2009 for hitting a taxi driver, and was accused of firing a gun at his sister's boyfriend in 2011 (although the charges were dropped due to lack of evidence).
After all of those incidents, Talib was suspended for four games on October 14th, 2012 (this season) for violating the league's policy on performance enhancing drugs (Talib admitted to using adderall without a prescription). As Talib is currently suspended, he will be unable to join the Patriots until after Week 11 as the Patriots are on a bye week and Talib has one game left to sit out.
Talib has starting quality and should Bill Belichick and the Patriots locker room keep him under control, using a 4th round pick to grab a starting corner, even in the last year of his contract, could prove to push the team's defense over the top as they head into the season's final stretch.
Looking at the value chart, should the Patriots make it to the second round of the playoffs, and should the Buccaneers remain in the 10-15 range overall, the overall value of Talib + 7th vs 4th places Talib at approximately an early 5th round pick.
The Patriots currently have a 1st, 2nd, 3rd, and two 7th rounders as they traded away their 4th for Talib, their 5th for Albert Haynesworth, and their 6th for Chad Ochocinco. Hopefully Talib doesn't join those names with respect to his performance on the field.