PITTSBURGH -- The reigning Stanley Cup champions have suffered a massive blow as they soon begin their title defense. The Pittsburgh Penguins announced Wednesday that No. 1 defenseman Kris Letang will be out four to six months following surgery for a herniated disc in his neck.

"Kris underwent an MRI in February that revealed a herniated disc in his neck," general manager Jim Rutherford said in a statement. "Our neurosurgeons examined him and recommended conservative treatment in an attempt to correct the condition without surgery. Kris had been making progress and was hopeful of returning for the playoffs until about a week ago, when the progress plateaued. He underwent another MRI, and, at that point it was determined that surgery was needed."

Letang thanked fans for their support on Wednesday.

I just want to say thank you to everyone for all the kind words!! I will be back stronger than ever !! pic.twitter.com/wVK2DWgcmy — Kristopher Letang (@Letang_58) April 5, 2017

Letang has missed the past 20 games. He had 34 points (5 goals, 29 assists) in 41 games this season and as expected was one of the major contributors last spring when the Penguins won the Stanley Cup.

The Penguins did add a pair of defensemen in Mark Streit and Ron Hainsey before the trade deadline, but there's no replacing Letang, a five-time All Star and perennial Norris Trophy candidate.

Letang had 67 points during the regular season last year and added 15 points in 23 games during the playoffs.