-Your stats will start decaying if they are not at 30, 50, or 70 in Career mode, unless an attribute point is added to them before the yellow bar completely disappears. The yellow bar represents how close each stats is to decaying. Monitor your stats and either leave them at 30, 50, or 70, or assure that you add at least one attribute point to them before the yellow bar disappears and they begin decaying each week.
-Once your created fighter's stats are at 100 in Career mode, get all desired stats to 70, 50, or 30 to prevent the stats from decaying below those levels. Then, accumulate as many points as possible from Free Sparring and save them until Career mode is almost over in 2021. Note: You must fight for twelve years. Then, use your saved attribute points to increase your fighter's stats as desired. Once Career mode ends, you can still use your created fighter in other modes, including online. By doing this, you won't lose stats due to decay and will have a fighter with high attributes after Career mode is over.