Updated

Patriots linebacker Dane Fletcher tore the ACL in his left knee in the first quarter of Thursday's preseason opener, according to Ian Rapoport of the NFL Network. Fletcher started the game at inside linebacker for the Patriots - filling in for Brandon Spikes - and was part of a unit that forced a three-and-out on Drew Brees and the Saints.

Then, as the Patriots first drive stalled, he returned to the field on the punt unit. He fell to the turf and needed help to get off the field. Fletcher was taken to the locker room, where the diagnosis was made.

"It's unfortunate," said fellow Patriots linebacker Rob Ninkovich, whose locker is next to Fletcher's. "You hope for the best. You don't know what it is right now. I've been through some knee injuries and I know kind of how that goes. You don't really know until you see a specialist or get an MRI. I don't want to jump to conclusions on anything. It's always tough to have injuries in the preseason. I know Dane. He's a fighter so whatever it is, he's going to work hard and he'll be back."

The punt wound up not counting and the Patriots gained a first down on the play as the Saints were called for a procedure penalty.

Fletcher has proven to be one of the most versatile players in the Bill Belichick defensive system, playing both inside and outside linebacker. He finished his 2010 rookie season with 23 tackles and two sacks in 13 games played, all as a reserve. In 2011, Fletcher had 37 tackles as his role grew. Fletcher was limited last season due to a thumb injury that kept him out for six weeks. In Super Bowl XLVI, he recorded one tackle.