Source: Tully Banta-Cain has surgery

Veteran New England Patriots outside linebacker Tully Banta-Cain underwent a surgical procedure on his abdomen on Friday, a source confirmed, while estimating a four-to-five week recovery period.

The source said Banta-Cain had sustained the injury last season, and in meeting with team doctors at the end of the year, it was decided that no surgery was required. But Banta-Cain tweaked the injury in recent workouts, the source said.

Missing five weeks would place Banta-Cain's status for the Patriots' season opener Sept. 12 at Miami in serious jeopardy.

Banta-Cain, one of the Patriots' top pass-rushers, enters his ninth NFL season. He played in 15 games in 2010, with six starts, and was second on the team with five sacks. His role was mostly as a pass-rusher in specialty packages.

In 2009, Banta-Cain proved to be one of the best NFL bargains in free agency, joining New England on a modest one-year contract and finishing with 10 sacks. The Patriots inked him to a three-year extension last offseason and Banta-Cain is scheduled to earn a base salary of $2.3 million in 2011, with a salary cap charge more than $4 million.

The outside linebacker/rush end position in the Patriots' 3-4 scheme has six-year veteran Rob Ninkovich and 2010 second-round draft choice Jermaine Cunningham returning atop the depth chart. Veteran Eric Moore, a late-season signing in 2010, also projects to be part of the mix, with longshot Marques Murrell and 2011 sixth-round pick Markell Carter rounding out the depth chart.

When combining Banta-Cain's health and the Patriots' failure to target the position early in the draft, this could be an area the team eyes in veteran free agency.

Mike Reiss covers the Patriots for ESPNBoston.com.