The Philadelphia Eagles acquired linebacker Will Witherspoon from the St. Louis Rams on Tuesday for rookie wide receiver Brandon Gibson and a fifth-round pick in 2010.

The Eagles made the trade to get Witherspoon, an eight-year veteran who spent his first four seasons with Carolina. He was the Rams’ starter at the weakside spot and had 36 tackles.

Witherspoon has recorded more than 100 tackles three times in his career and has missed only two games due to injury.

Gibson, a sixth-round pick from Washington State, was inactive for all six games so far.

Police add to McNair saga

Ex-NFL quarterback Steve McNair’s mistress exchanged messages for weeks with the man who sold her the gun she used to kill McNair and herself, police said Tuesday.

The findings came a day after investigators released 50 text messages between McNair and Sahel Kazemi they say supports their conclusion of a murder-suicide because she was desperate over money and feared their relationship was ending.

Police spokesman Don Aaron said Kazemi also was in contact weeks before the July 4 killings with Adrian Gilliam, who pleaded guilty to gun charges for selling the weapon to her.

Extra points

Jason Campbell will remain the Redskins starting quarterback. … Joey Galloway’s brief stint with the Patriots ended as the 15-year veteran wide receiver was released. …Cleveland linebacker D’Qwell Jackson will miss the rest of the season because of a shoulder injury. … The Jets placed nose tackle Kris Jenkins on season-ending injured reserve, and re-signed defensive tackle Howard Green. … The Carolina Panthers have waived defensive tackle Antwon Burton, creating a roster spot for newly acquired defensive tackle Tank Tyler. The Panthers sent their 2010 fifth-round pick to Kansas City late Monday for Tyler, who is expected to split time with Hollis Thomas at nose tackle.