This just happened to me last night. Was in season 4 with the club (they were terrible the previous 3!), and had a one year contract for $4.5M as an Ace starter (finished the season with a record of 26-1 with 570 SO and an ERA of 0.13).
After winning the division series my player was dropped to AA. The swift kick in the nether regions is that my team won the world series without me and the season ends....
Fast forward through off season and the club tries to offer me a payrate equivalent to a AA starter for one year (since that is where they placed me), of $2.2M. I countered back with $5.5M for one year and it went to arbitration where I seem to have won my case.
It just leaves a sour taste that you cant get rid of especially since you grind through 4 seasons for nothing...