Since you need to have a unique name for each five members of a team does this mean that each team will only have a max of 5 members? If this is the case then you could do this a few ways. One way would be to have a team table that is separate from the users table. In this team table you can just have an id column, a name column, then a member column.
Doing it this way you would create a new team, then you can insert the users into their table and have an update for the team table that will add in the member for each insert that occurs for the users table. You would be just inserting the id of the newly inserted user into the team table.