Today, Yahoo Sports reported that 49ers linebacker Patrick Willis is retiring at the age of 30. It was a surprise to many that the five-time All Pro and seven-time Pro Bowler would retire with seemingly more good years ahead of him.

With the severity of the physical trauma of football becoming clearer and clearer by the day, I wonder if more and more players will choose to retire earlier in their careers, after accumulating some threshold of wear and tear and/or wealth.

Economically, it makes sense. A star player can make many tens of millions of dollars in a the span of a short career, and even a regular starter can pocket millions. If you are frugal, you'll achieve a very comfortable nest egg. At that point, is each additional marginal million dollars worth perhaps several years of your life, or a remaining lifetime of debilitating pain, or worse?

The more we hear about players suffering terribly in their old age, the more the cost side of the economic equation increases. Given that data, more and more will come to see just how rational Willis' decision is.

UPDATE (16 Mar 2015): Chris Borland of the 49ers announced today that he's retiring after just one season, and a great one, because of concerns over the impact of repetitive head trauma on his health. It's happening even sooner than I anticipated.

"I just honestly want to do what's best for my health," Borland told "Outside the Lines." "From what I've researched and what I've experienced, I don't think it's worth the risk."

Borland becomes the most prominent NFL player to leave the game in his prime because of concerns about brain injuries. More than 70 former players have been diagnosed with progressive neurological disease following their deaths, and numerous studies have shown connections between the repetitive head trauma associated with football, brain damage and issues such as depression and memory loss.

"I feel largely the same, as sharp as I've ever been. For me, it's wanting to be proactive," Borland said. "I'm concerned that if you wait till you have symptoms, it's too late. ... There are a lot of unknowns. I can't claim that X will happen. I just want to live a long healthy life, and I don't want to have any neurological diseases or die younger than I would otherwise."