That right there is the biggest issue keeping overall earning potential down for baseball players. Owners are essentially getting free, extra minor league years due to the reliance on college baseball. If a player stays in college for 4 years, plus the minors for an average of 2 or 3 before getting called up, that means he is already 24, 25 years old. If a player peaks at age 27, 28, then their best seasons were during club control or arbitration years, allowing the owners to bypass paying a large free agent contract. The additional info about big statistical fall-off after age 32, also shows another reason free agency has become depressed. The MLBPA will need to fight for free agency after 3 or 4 years and/or better pay for upper level minor leaguers (AAA, AA). Otherwise, I see the depression of salaries continuing. It also becomes a depression/reduction in 'star power' and marketing for the game.
SI.com report citing ESPN and MLB.com --> Martin Maldonado was offered a 2-year deal from the Astros at the start of the offseason, but has since changed agents from Scott Boras to Dan Lozano, so it is unknown if that offer is still available.
