Every healthy player comes with some injury risk, and there's an aspect of luck - or lack thereof - in determining who goes down and who gets through the season largely unscathed. However, factors such as position, workload, age, body-type and injury history do significantly tilt the odds. Entering the 2013 season let's examine a few players at each position on the extreme ends of the spectrum - both the most durable and the most fragile. (Players who are not expected to be healthy for the start of the season are not included.)
Quarterback - The Durable
New Orleans Saints
Brees has started 111 of a possible 112 regular season games since signing with New Orleans. His lone missed game came in Week 17 as he was rested in preparation for the Saints' eventual run to a Super Bowl win. His quick release and few rush attempts ensure he does not expose himself to unnecessary collisions.
Age factors in here, as Dalton is the youngest quarterback on the list. At 25, he's never missed a start since taking over as the primary signal caller for Cincinnati in 2011. He's played through some minor injuries but nothing considered significant. A right knee injury cost him two games in college but has not been an issue in the NFL.
The reigning Super Bowl MVP has never missed a game in his career and has nearly avoided the injury report entirely. Teammate Ray Rice has been vital in keeping Flacco healthy, providing a steady running game, a reliable check-down option and timely blocking in the backfield.
New York Giants
Manning has appeared in every Giants game for eight consecutive seasons. He rarely leaves the pocket, as evidenced by his 20 rushing attempts last season. The Giants offensive line improved last year as Manning was sacked just 19 times, nearly 10 fewer than in 2011.
Turf toe cost Ryan two games in his second season, but for the most part he's avoided the injury report ever since. He did suffer an AC sprain to his non-throwing shoulder in the NFC championship game, but the arm is fully healed entering the new season.
Quarterback - The Fragile
A change of scenery does little to decrease the risk surrounding Palmer. He's had elbow and shoulder issues since his mechanics changed following 2006 surgery to repair a torn ACL and MCL in his left knee. He's also had issues with both thumbs, and his 2012 season ended prematurely after he suffered broken ribs and a bruised lung. Moreover, the Cardinals offensive line (though improved this offseason) was among the worst in the league last year.
Green Bay Packers
Rodgers inclusion on this list may come as a surprise, but his style of play and poor offensive line raise some red flags. Rodgers has been sacked 202 times in the last five seasons, including a league-high 51 times last year. Not an encouraging stat for a player who has endured multiple concussions and several other bumps and bruises.
Roethlisberger has played 16 games just once in his nine-year career. In that span he's been sacked 344 times and missed time due to an appendectomy as well as shoulder, hand and knee injuries. Roethlisberger reminds me of Steve McNair, another big-bodied quarterback who endured countless injuries. He's as tough as they come but prepare for him to miss at least one game.
Stafford's first two seasons in the league ended with an injured reserve designation following knee surgery in 2009 and right shoulder surgery in 2010. He's also managed lower extremity muscular injuries and a fractured right index finger. He may have attempted an NFL-record 727 passes last season, but that also means he was exposed to the pass rush more often than any other signal caller.
This should come as no surprise as Vick has become a permanent fixture on the injury report. The former Pro Bowler has endured a broken fibula, a quadriceps contusion, multiple concussions, broken ribs and other various sprains and strains throughout his 10-year career. He's as risky as they come.
Running Back - The Durable
Maybe it's the steady diet of Skittles that has kept Lynch running so smoothly despite his aggressive style of play. He split carries early in his career, which may have saved his body from enduring the normal wear-and-tear associated with a feature back. The addition of rookie Christine Michael could help keep Lynch fresh.
Morris' size, body type and age suggest he'll avoid time on the sidelines as a sophomore. He beat out fellow second-year running back Doug Martin for a spot on this list due to a cleaner bill of health during college.
This was a tough call, but Peterson's incomparable return from ACL and MCL surgery helped erase doubts. Doctors and medical professionals call him a physical freak, and it's hard to argue against a guy who has missed only seven games in his six-year career. Furthermore, most players recovering from this type of surgery don't return to full strength until their second year back. If that trend holds true, Peterson could be in line for a second straight MVP award.
Rice has appeared in 77 of a possible 80 games since entering the league and has not missed a game since taking over the feature-back role. He's carried a heavy load for Baltimore but has shown no signs of wearing down.
Spiller is another back that has benefited from splitting carries early in his career. He's also taken advantage of multiple leg injuries to older teammate Fred Jackson to prove he's capable of performing at a high level. Additionally, his speed and explosiveness allow him to avoid potential tacklers, saving his body from excessive hits.
Running Back - The Fragile
San Francisco 49ers
The 30-year-old Gore likely will receive his 2,000th career rushing attempt in 2013, and a decline in productivity seems inevitable. He's needed multiple major surgeries throughout his career on his knee, shoulders and hips, and his body has absorbed more contact than other top running backs.
Jones-Drew shouldered a heavy load prior to last season's injury-shortened season. In the three years prior to 2012, he averaged 318 carries before missing 10 games with mid-foot fracture that ultimately needed surgery. Foot injuries are particularly hard to bounce back from for running backs, so tread carefully here.
San Diego Chargers
Multiple lower extremities injuries are recipes for disaster, and Mathews has already suffered groin, foot, ankle and toe problems. It gets worse, as he missed time last season after breaking both his left and right collarbones at different points of the season.
When he's healthy he's been fantastic. Unfortunately he's struggled to stay on the field, missing time with a Lisfranc sprain, a high-ankle sprain and turf toe. A running back with bad wheels will always be a risk no matter the potential.
Murray fell to the Cowboys on draft day because of questions about his durability. He's produced for Dallas but has failed to shake the lingering doubts about his ability to stay healthy. A broken ankle and a foot sprain have prevented him from being an elite fantasy weapon.
Wide Receiver & Tight End - The Durable
Fitzgerald has appeared in 84 consecutive regular season games and been a fixture in the Arizona offense. The revolving door at quarterback may have limited his productivity, but his health has never been a concern. He's no longer a young up-and-comer, but the veteran shows no signs of slowing down.
Age is huge factor for durability in wideouts, and Green has Father Time on his side. The 25-year old has bounced back quickly from several minor injuries and will look to continue his promising career in his third season as a pro.
Marshall has managed to stay on the field despite playing for three teams in four seasons. He addressed a minor hip injury following the season but has bounced back from a similar procedure before. He will be 29 entering training camp and still has several productive seasons ahead of him.
Wallace's Week 17 absence due to a hip strain was the only game he's missed in his four years with Pittsburgh. He now heads to Miami with a clean bill of health and a relatively clean injury history. The perfect blend of age and experience has him poised to enter the prime of his career.
Limited reps early on have helped preserve the veteran's body, and White has not missed a game in his previous eight seasons. Additionally, the emergence of Julio Jones should only help extend his career. White's managed to stay productive even while dealing with the occasional nagging injury.
Witten has not missed a contest since his rookie season when a broken jaw cost him his one game. Not even a spleen injury suffered in preseason could keep Dallas' iron man off the field. The eight-time Pro Bowler remains a valuable and trustworthy option.
Wide Receiver & Tight End - The Fragile
At a position that requires speed and explosiveness, muscle injuries in the lower leg can be a receiver's worst enemies. Unfortunately, this is a problem Austin knows all too well as he as dealt with chronic hamstring problems as well as hip flexor issues. He spent a second straight offseason focused on improving his flexibility, but he remains a precarious pick.
San Diego Chargers
Gates has not played in all 16 games of a season since turning 30 in 2010. Chronic problems with the plantar fascia in his right foot have been the primary culprit behind Gates' missed games, but a rib injury and toe and ankle problems have also played a factor.
Harvin failed to build on his 2011 campaign with injuries once again limiting the talented receiver. He suffered a severely sprained ankle last year and has previously dealt with a lower leg fracture in addition to migraine headaches throughout his career. He's in a better situation in Seattle, but he'll have to stay on the field to be effective.
Johnson has spent 10 years in the NFL and will be 32 at the start of the 2013 season. He's missed time with hamstring injuries in both legs, undergone knee surgery and battled a lingering groin injury for a majority of last season. He may be talented, but he comes with a high degree of risk.
New York Giants
Nicks is young receiver with only four years in the league, but he's never played in all 16 games and has needed surgery in consecutive offseasons. His surgically repaired foot was an issue for much of last year before a knee injury ended his season. Both injuries can become chronic problems, elevating his risk.
Smith has had a long, productive career but has managed to amass multiple injuries along the way. He's endured fractures to his arm and leg as well as various muscular injuries. The team has previously given him practice days off to rest, and we should look for that trend to continue this season.