Players who are 30+

[onejayhawk]

Bill James once said that fans do not understand how fast players age. For a player to even be active after age 30 is a mark of achievement. Indeed, GP and IP are two of the very best indicators of player quality. So, when projecting stars on the downslope, how do you adjust? For example, take Andrew McCutchen (30), Jose Reyes (33), Ian Desmond (31) and Adrian Beltre (37).

McCutchen was once a 30/30 threat. This season he was not even a top 100 player. He is the youngest of the four by over a year.
Desmond had a huge bounceback season. Moving from SS to OF was an unqualified success.
Reyes was hurt most of 2016 and moved to a worse hitter's park. Yet, his numbers were close to 20/20 rates and in line with his main career averages.
Beltre is the senior citizen of the bunch. Once again, he produced a HoF season (.300/30/100), his second since he was McCutchen's age.

All are free swingers. How do you adjust for increasing age for players like this?

J

[virgonomic]

I bid to about 80% of projected value and let someone else take the risk beyond that.

[rhd]

I dont start discounting player value until age 34. Most players dont seem to begin a significant decline until then or after.