The three stars might be easier to sell. The guys at 5, only your level and above will see, and they might not look like an upgrade at this point in the season. Especially if they are single role and that single role is MC. Also if they have bad ratings they will be hard to sell.. and at your level there is less managers overall, and those are savvy buyers. The guys I can't move almost always sell on day 1 since then their ratings can't be seen... and everyone is looking at that time, cause right now most have their team built and are only doing emergency purchases to cover injury, though bargain hunters wishing to avoid bid wars are shopping now, too. Make sure to put them up for sale at every time of day possible - the busiest time on your server might be when you are asleep. Sometimes if they are very old you might have to consider sacking them.

Keep trying, and good luck.