DeAngelo Hall defends hit during Twitter exchange with Bills' Chris Gragg

Washington Redskins safety DeAngelo Hall defended a low hit that injured Buffalo Bills tight end Chris Gragg in Friday's preseason meeting between the two teams, telling Gragg in a tweet Saturday that he targeted his legs because the NFL would have fined the veteran defensive back for tackling Gragg too high.

Gragg, a fourth-year tight end who started four games last season for the Bills, announced Saturday on Instagram that he's out for the season because of a left knee injury suffered on the play.

Hall lowered his shoulder into Gragg's left leg after the tight end made a 5-yard catch over the middle of the field in the second quarter of Friday's game. Gragg later walked off the field under his own power, but coach Rex Ryan said after the game that doctors suspected Gragg suffered a serious ACL injury.

"It's a real shame," Ryan told reporters. "Sometimes, especially with Gragg's injury, a guy should make a tackle. But I get it. Was frustrated he just had a 15-yard penalty. That was ridiculous in my opinion, but it is what it is."

Prior to his exchange Saturday with Gragg, Hall defended his tackle on Twitter later Friday night.

Gragg caught a career-high 12 passes last season for the Bills, totaling 150 yards. The 2013 seventh-round pick has played in 32 career games for Buffalo, making 10 starts.