The good news is that New Orleans has good depth at the position. Veterans Manti Te'o and Craig Robertson have done a nice job filling in for Klein when he has missed time this year, including most of the past two games.
The exact nature of Klein's injury is unclear. He suffered the injury during the first half in a 20-17 loss at Atlanta on Dec. 7 and did not play last week against the New York Jets. It's unclear if Klein suffered a setback or if the Saints just determined he would not return in time to help them even if they make a deep playoff run.
Klein, 26, has been a great addition for the Saints this year after they signed him away from the rival Carolina Panthers on the first day of free agency. Though he was mostly a backup behind Luke Kuechly and Thomas Davis in Carolina, he has been a full-time starter and signal-caller for the Saints while playing both middle linebacker and strongside linebacker. And he was elected as a team captain by his teammates in his first summer with the team.
Klein had 54 tackles, 2 sacks, 1 forced fumble and 4 pass defenses in 12 games played this year while helping to lead the Saints' remarkable turnaround on defense. They rank 11th in the NFL in yards allowed and tied for ninth in points allowed.
He was on the field for both of New Orleans' victories over his former team, Carolina, which has given the Saints a slight edge in the tight NFC South race so far, since both teams are 10-4. But there is still a lot to be decided with the Falcons (9-5) at New Orleans this Sunday.
Te'o has also been a solid free-agent addition for the Saints after spending his first four years as a full-time starter with the Chargers. He has played every game this year, starting eight games, with 53 tackles and two pass defenses.
Robertson is yet another veteran who has started at both middle and weakside linebacker during his six-year career with the Saints and Cleveland Browns. He has played in every game this year with 10 starts, 66 tackles, 2 sacks, 1 interception, 1 forced fumble and 3 pass defenses.
To fill Klein's roster spot, the Saints re-signed veteran tight end and special-teamer John Phillips. They've also had depth issues at tight end because of recent injuries to Coby Fleener and Michael Hoomanawanui.