Even the most durable, heavy-duty vehicle wears out the tread on its tires.
And eventually, no matter how high-octane the engine may be, you're forced to pull over and fix the issue before it's too late.
Joe Staley made that bitter, yet forward-thinking decision to turn off his motor on Tuesday. The San Francisco 49ers announced that the All-Pro linebacker would be placed on the Injured Reserve List and undergo season-ending surgery on his nagging left big toe, which has bothered him for several seasons.
"If you like to get on the pedal a little bit, you tell yourself you can't do that because if you do, you're going to blow your tire out," Willis said. "And that's kind of how I've been playing the last few years… Maybe at certain times people saw something uncharacteristic, but that's all because I was trying to find a way to compensate, to be able to continue to go out there and play.
"And it just got to the point where I couldn't put the torque or the force that I needed to continue to grow and be a better linebacker."
Willis' Pro Bowl-caliber play while battling pain speaks to the veteran's toughness. But after he aggravated the injury during the team's Week 6 win in St. Louis, the toe only got worse.
"When I hurt it in the Rams game it kind of made me a little nervous because I knew what I had been feeling all these years," Willis said. "I felt like the Lord was talking to me. I felt like he finally said, 'The time is now.'"
During the 49ers Week 8 bye, Willis fought valiantly to work his way back onto the field. The discomfort, however, proved too much to overcome.
"To most people, they might be like, 'Man, maybe Willis is losing a step.' But I promise you, physically and mentally, I'm just as good now as I was early on," Willis said. "Unfortunately, the things I need most to make me who I am are my feet.
"And without a big toe, it's like trying to grab without a thumb, you just can't do it. I don't care how strong you are."
That realization led Willis and the 49ers to opt for surgery, so the problem could be resolved once and for all. Willis is confident that the resolution, albeit a saddening one in the moment, will help extend his career in the long run.
"I feel like I have five or six more years of great football left in my body," Willis said. "But unfortunately this toe was telling me otherwise. That's the only thing that was weighing on my mind… It just didn't get better. So this was the route that was best."
Willis' absence means that rookie linebacker Chris Borland will continue to start at least until NaVorro Bowman returns. In his last two games, Borland has recorded 35 tackles and an overtime fumble recovery.
"I'm truly proud of the way he is playing," Willis said.
Willis is expected to have the procedure on his toe done in the next few days, and if he has it his way, the linebacker will get back to work shortly thereafter with the focus on being ready for Week 1 in 2015.
"The sooner we can get it done, the sooner I can get back into rehabbing and get back to form," Willis said. "It's going to take a while, but I'm optimistic. I like to say I'm one of the hardest working guys in this universe, on this planet."