[WORLD CUP COUNTDOWN] FIFA has set May 11 as the deadline for all World Cup finalists to submit a preliminary list of 30 players. The final list of 23 players (including three keepers) must be named by June 1, and those players must come from the 30-man preliminary roster.

Another key date: May 16, the end of play in Europe's major leagues. Most World Cup teams won't begin final preparations until after that.

After June 1 on, a player may be replaced due to injury up to 24 hours prior to a team’s first match. In this case, the replacement player is not required to come from the 30-man preliminary list.

Four years ago, FIFA set May 15 as the deadline for teams to submit their final roster. Its rationale was that players would know whether they would or would not be headed to the World Cup before they were granted a week's rest before final preparations began.