Old guys playing professional sports is fun, but unless we're talking about kickers in the NFL or left-handed relievers in baseball, guys in their late 30's don't generally perform all that well. It's an even trickier situation when those players are prominent members of their respective team's plan for the season. In the case of the Denver Broncos and the Dallas Mavericks, they're both counting on aging stars to help them succeed.

Dirk Nowitzki is 37 years old and finishing up one of the most accomplished careers in basketball history, both in the NBA and internationally. Peyton Manning is a surefire Hall of Famer who is currently, at 39 years old, getting some help winning football games and opening spaghetti sauce jars from his teammates as we question his arm strength. But here's something the Mavs have been kicking around in their locker room recently: who would win in a 40-yard dash?

Man, this would be ugly. That's first and foremost. Thinking about these two slugs hobbling down a track is truly painful. Manning has had serious neck surgery, he's close to 40, and his 40-yard dash time was 4.8 seconds nearly two decades ago. It's hard to imagine that would hold up. Nowitzki isn't exactly fleet of foot himself, and has had multiple knee injuries over the course of his career that cause him to walk about as stiff as those tree creatures in the Lord of the Rings movies.

Thanks to SportsVu data, we know his average speed in the NBA last season was 3.7 miles per hour when factoring in all movements (sprinting, walking, jogging, and standing). That was the slowest on the Mavs and one of the slowest averages in the entire NBA. It's tough to know if Manning could muster up the speed for 40 yards or if the long strides of the 7-foot German would be too much.

It reminds us of the Dick Bavetta-Charles Barkley race, and I'd imagine if Dirk and Peyton did the dash against each other, many of Dirk's teammates would have a similar reaction as Kevin Garnett did when addressing Barkley vs. Bavetta in 2007.

I'm going with Dirk on this one, but I'm not sure any of us lose if we get this race.

Dirk Nowitzki vs. Peyton Manning: Who you got? (USATSI)
Dirk Nowitzki vs. Peyton Manning: Who you got? (USATSI)