First, we need to set a benchmark to determine when running backs are still useful in fantasy football. We will use a scoring system of 1 FP per 10 yards rushing or receiving and 6 FP per touchdown. Over the last four seasons, the 24th ranked running back has scored an average of 148.75 FP. Therefore, we will use a 150 FP season as the cut-off.

Historical RB Production

The following table shows the data for eight running backs that have retired in recent years. The totals are up to and including the last season that the running back scored at least 150 FP. The one exception to this is Eddie George's 149 FP 2003 season, which is also included.

Exception to the rule: Smith was a fantasy relevant through age 35.

The number of career f/carries ranges from 1568 to 3921.5 (excluding Smith's mind-blowing 4666.5.) Again, this range is to great to be an effective prediction tool. The best we can say is that we should be careful when forecasting a running back to be effective after 3,000 f/carries since only six backs have accomplished this feat in the past.

The range of ages falls into a much tighter grouping, with 11 of the 18 players having their final productive season at the age of 30 or 31. If the range is expanded to 29 to 32, then it includes everyone except Smith and Allen.

There is quite a range in the number of career games played, from 102 for Priest Holmes to 226 for Emmitt Smith. Even if we remove a few outliers, the range looks to be too great to make any reasonable forecasts. Similarly, the number of heavy workload years ranges from zero for Charlie Garner to 10 for Walter Payton. Thus, no clear trends are apparent for the number of games played or the number of heavy workload years.

Conclusions

As we have seen, heavy workload years may be a good indicator of a drop in fantasy production for the next year, but it there is not a correlation between heavy workload and the end of a fantasy running back's career. With four exceptions (Smith, Allen, Walter Payton, and Jerome Bettis), the best indicators for the end of a successful fantasy career appear to be age, the number of seasons played, and the total number of f/carries. Of these three factors, age (30 to 31) looks to be the best prognosticator with upper limits provided by seasons (10) and f/carries (3,000).

Predictions for 2008

Now that we have looked at the past, let's make some predictions for the future. As of opening day, there will be eight running backs that are 30 or older and have or have had fantasy relevance. Of these eight, three will probably not get drafted in most leagues. They are Ahman Green, Reuben Droughns, and Shaun Alexander. Green is in a crowded backfield already bothered by a groin inury, Droughns is buried on the depth chart, and Alexander doesn't even have a team at this time. The other five running backs are Edgerrin James, Thomas Jones, Fred Taylor, Ricky Williams, and Warrick Dunn.

Edgerrin James - James has been solid but not spectacular since moving to the desert. FFtoday currently predicts he will have 184 FP in 2008, placing him 15th for running backs. Unfortunately for him, he is 30 years old, entering his tenth season, and has 3,058 career f/carries. That puts him at twelfth all time for most f/carries. Two (age and number of seasons) of our tools say this will be his last productive year. One (career f/carries) says the end has already come. Expect this to be Edge's last year of fantasy relevance.

Thomas Jones - Despite a slow start to his career, Jones has turned into a productive back. Current predictions call for him scoring 161 FP, good for 22nd place on the running back list and making him a decent #2 fantasy RB. He is 30 and entering his ninth season, so he might have two more years left in him.

Fred Taylor - Although known in fantasy circles as “Fragile Freddy”, Taylor has started 14 or more games in five of the last six seasons. He is also 32 and entering his eleventh season. Taylor may be the exception to the “31 or 10 seasons” rule, but history says you should not count on it.

Ricky Williams - Unless there is an injury to Ronnie Brown, Williams will not be starting in 2008. He still has value as a handcuff, but his days of fantasy glory look to be over. Due to his time out of football for partaking of various recreational herbs, his number of seasons played and career f/carries are low, but his age (31) can not be denied.

Warrick Dunn - Like Williams, Dunn still has fantasy value as a handcuff or bye week fill-in, but his starting days are over. His age (33) and number of seasons played (11) show that 2006 was his last hurrah in fantasy circles.

Keeper and Dynasty Leagues

There are seven significant running backs that will be 29 by the end of the season. They are LaDainian Tomlinson, Jamal Lewis, Rudi Johnson, Brian Westbrook, Larry Johnson, Deuce McAllister, and Ladell Betts. I don't mean to suggest that these players should be traded for pennies on the dollar, but Shaun Alexander has shown us just how quickly fantasy fortunes can change for a player. Given their situations, I would probably look to trade high at the first reasonable opportunity with Larry Johnson, McAllister, and Betts. I would be more tempted to keep the others for another year or two. Just remember that these players will probably be leading teams to fantasy glory for at most three more years.