The age-old question in the NHL

At 39 years old, Mike Knuble is still producing at a high level for the Capitals. Graig Abel/NHLI/Getty Images

It was hardly a surprise when Nicklas Lidstrom decided to return for a 20th NHL season. After all, he had led the Detroit Red Wings in ice time per game and was the first 40-year-old defenseman to score 60 points in an NHL season -- en route to winning his seventh Norris Trophy despite playing the toughest competition and starting in the defensive end most of the time.

"[Lidstrom is] one of those guys that's a freak of nature, the shape he's in," teammate Niklas Kronwall said to Michigan media upon hearing Lidstrom would return for another season. "We're so spoiled having a guy like that around."

Lidstrom no doubt has kept Father Time on the other side of the boards, but if you examine NHL history, you'll notice that a player's productivity starts to wane as he ages.

A few other exceptions to the rule, however, prove that a 35th birthday doesn't signify the end of a career.