Based on my understanding of your concept I will do this using a combination of MySQL to power the database, PHP for functionality and HTML (backed by custom graphics) to provide an appealing user experience.
The Back end development.
I will create a MYSQL database with tables for users, messages, leagues, teams and stats, players.
Users will include information on user ID, Username, Password, Email Address, and if the character is as an Admin or not.
Messages will have a unique ID, TO, and the message itself.
Leagues will have a unique league ID as well as a name.
Teams will have a unique team ID as well as a name, captain, league belonging to, list of players, currency and overall score.
Stats will include a unqiue Id, player associates with and all stats listed in your google document.
Players will include a unique ID, name.
-------
From there I will create a PHP Admin Menu that will allow you to View/Create/Edit/Delete leagues, teams and players. This will give you ultimate control over everything available to a user. As well as a page to enter recent player stats.
On the user side will be a login/register/join league page, team and player profiles (to include stats and scores) and the ability to use currency, trade/loan players.
At this point you can test the script to ensure it has the functionality you need before I proceed.
Up until this point it's all just text on a page. Once you've approved the script functionality, I will create the design.