Mario Williams en route to visit BillsMarch 13, 2012 - 4:57 PM | 3 commentsBuffalo Bills may be getting aggressive in free agency like never before in their history.Houston Texans defensive end Mario Williams is en route to visiting the Bills tonight, the News confirmed. ESPN reported it first. Williams is the top defensive player available in free agency and probalby will command the highest salary for a defensive player in NFL history. His deal may eclipse the one Chicago gave to defensive end Julius Peppers, which called for $42 million in guaranteed money over the first three years.Meanwhile, reports indicate the Bills also have a visit scheduled with New Orleans receiver Robert Meachem.Bills General Manager Buddy Nix has said for a couple of weeks the Bills would be aggressive in free agency. But Buffalo never has gone after a target as prominent as Williams. Buffalo's biggest previous free-agent signing was guard Derrick Dockery, who got a $7 million-per-year deal in 2007.Williams, 6-foot-7 and 290 pounds, was the first overall pick of the 2006 NFL Draft. He has 53 sacks in six seasons. He had 14 sacks in 2007, 12 in 2008, nine in 2009, 8.5 in 2010 and five in five games in 2011. Williams missed the last 11 games of last season due to a torn pectoral muscle. However, he is fully healthy now. The Texans entered free agency with only $1 million in space under the salary cap and were in no position to re-sign Williams.Meachem, 6-2 and 214, would fill the Bills' need for a big outside receiver to complement Stevie Johnson. Meachem was a first-round pick in 2008 and has an impressive combination of size and speed. He ran a 40-yard dash time of 4.39 seconds (Lee Evans speed) coming out of the University of Tennessee. He has averaged 43 catches and 6.6 touchdowns over the past three years. He had 45 catches for 722 yards in 2009, 44 for 638 yards in 2010 and 40 for 620 yards last season.The Bills entered free agency with about $19.5 million in space under the salary cap, according to News figures. Only about eight or 10 teams had more space. The Bills had about $34 million in cash space under the cap. Teams can spend over the cap in actual cash but not in "cap dollars." Cap dollars includes amortized signing bonuses for all players on the roster, not just money spent this year.