They are just normal players that are listed as almost at the next star. If they are young, and in the position you want, it can be worth spending 10-15 tokens on getting that play you need in early, without having to go through the bidding war for it.
I do think that bids should be cancel-able tho, having your tokens tied up, not knowing whether it will be accepted is annoying - I went out and bought another defender last year while my offer was a short time to finish (thinking I wouldn't win) - and I got the player and paid a lot more for the weaker player in the end. If I could have cancelled it, I would have.