Patriots won 3 out of 4 SuperBowls (2001, 2003, 2004) but have failed to win a SuperBowl since Logan Mankins was drafted in 2005.
Before Mankins was drafted, the Brady/Belichick led Patriots were a perfect 10-0 in the post-season and had the longest post-season winning streak of all time.... The same season Mankins was drafted, the Brady/Belichick combo lost their first ever playoff game.
Since Mankins was drafted, the Patriots have had arguably better teams(2007) than their SuperBowl years. However they've lost 3 conference championships and 2 SuperBowls. They've been so close to getting that 4th ring. That 4th ring that would cement Brady as the premier QB of all time and would forever end the Brady/Manning debate. That 4th ring that would shut up all the spy-gate haters.
Don't get me wrong. Mankins was/is a great player. But the Pats haven't won a SB since he's been on the team. I call it the Curse of Mankins. Now that he's gone, the Patriots will finally get that elusive 4th ring.