There couldn't have been a more polarizing hire for the San Francisco 49ers than Chip Kelly. David Neuman has already written an article about some of the myths that surround him. One of the the most fascinating and highly guarded secrets about Kelly's program is his strong belief in the positive effect sports science has on his players. Before the arrival of Kelly in Philadelphia, Andy Reid had instituted Taco Tuesdays and Fast Food Fridays. Kelly arrived and the menu at the Eagles training center was completely overhauled as was each player's daily routine. The Eagles backed this program with over $1 million in equipment and technology.
Yes, players had plastic cups at their locker everyday for daily urine analysis to measure hydration. Yes, players wore devices that contained a GPS, accelerometer, magnetometer and gyroscope to record every movement made by the wearer. Yes, players wore a heart monitor to track how much sleep they were getting. Yes, they had personalized smoothies that corresponded to all of the data acquired by these devices/methods. The amount of work/rest for players during practice was also adjusted with this information.
Is this intrusive? Maybe. One anonymous player claimed that these methods were "Orewellian," but if these methods keep players feeling fresh late in the season when every other team is deteriorating, isn't it worth it? Veteran players Todd Herremans, DeMeco Ryans and Trent Cole all told Kelly that they had never felt better in December.
These methods obviously can't prevent ACL injuries or broken bones, but what they can do is help players reduce the limiting effects of a problem hamstring or calf strain that can potentially keep them sidelined for weeks.
Football Outsiders has a metric called adjusted games lost (AGL). In simplified terms, it tracks how many games are lost by individual players to injuries. In 2013, Kelly's first year in Philadelphia, after implementing his sports science methods, the Eagles had the best AGL rating in the league. That same season, the Eagles also averaged the most snaps per second: one per every 23.38 and ranked 13th in their offensive play count. In 2014, Kelly's 2nd season, the Eagles were ranked 5th best in AGL and ran the most offensive snaps in the league (1127). This was all after being ranked 18th in 2012 prior to Kelly's arrival while at the same time running the 6th most plays (1079). Also important to note that the Eagles ranked last in time of possession in both 2013 and 2014, so while running a high number of offensive plays, the defense spent more time on the field than any other team, 2 seasons in a row, while still maintaining a top AGL ranking.
The significance of the AGL ranking vs. play count is pretty logical. The more plays run, the more "mileage" your players accumulate throughout the season, hence more exposure/possibility for injury. For example, in 2013, Denver racked up the most offensive plays (1156) and ranked 24th in AGL. In the same year New England ran the 2nd most plays (1138) and ranked 29th in AGL.
Just for perspective, San Francisco's AGL ranked 23rd in 2013 and 28th in 2014, but in 2012 when the 49ers went to the Super Bowl, the 49ers were ranked 1st while ranking 30th in amount of plays (969). It's no secret, if you keep your best players on the field, you have a better chance of winning.