What does 'Update Team Value' do?
However, when you sell a player, you are redeemed the amount you paid for them - whether their current value is up or down.
So, if your player has gone up in value since you bought them, and you then sell them, you will effectively make a loss if you try to buy them straight back again. You might not even be able to afford a player you just had in your squad! So take care when selling players...
On the other hand, if your player has gone down in value since you bought them, because you are always redeemed the value you paid for a player when you sell them, you could make a profit by selling such a player and then buying them straight back again.
To save you the trouble of doing this, you can hit the Update Team Value button. This feature redeems you the difference in a value between a player's original cost and their current value, if the latter is lower.