England manager Roy Hodgson will name his 23-man party for the tournament in Brazil at 2pm.
Before he travels up to Luton, where the announcement is being made at the home of sponsors Vauxhall, he will call 23 players and give them the best news of their careers.
The likes of Steven Gerrard, Joe Hart and Wayne Rooney will be told they have made the cut for a once-in-a-lifetime event - a World Cup in Brazil, the spiritual home of football.
But for Ashley Cole, Frank Lampard, and several more experienced England players, they will be much more nervous when they answer the England manager's call.
Hodgson is not looking forward to breaking hearts.
"There's only one downside to this job and it's a major downside," Hodgson said.
"I can only take 23 players. And there are more than 23 I'd like to take with me. It's not the most pleasant part of the job."
All eyes will be looking to see whether Cole or Shaw has made the 23.
Cole is England's most-capped tournament player.
The 33-year-old, who has 107 caps in total, has started every game since making his finals bow in the 2002 World Cup against Sweden.
But he may not be part of Hodgson's plans for Brazil thanks to the emergence of teenage sensation Shaw.
Shaw, 18, was voted into the Professional Footballers' Association team of year by his peers last month after an impressive season with Saints.
With Leighton Baines certain to go to Brazil, Hodgson will be left to choose between Cole and Shaw, who only made his England debut against Denmark in March.
When asked about Cole's failure to hold down a first-team place at Chelsea this year, Hodgson said recently: "Well the fact that he had not played won't affect me that much."
Hodgson has not ruled out taking all three left-backs, but that is unlikely.
Cole's Chelsea team-mate Lampard, who has 103 caps, will also be a nervous man when Hodgson calls tomorrow.
The emergence of Jordan Henderson and Ross Barkley has put pressure on Lampard, who is no longer assured of a first-team place at Stamford Bridge.
Barkley, Shaw, Henderson and Liverpool teenager Raheem Sterling have breathed fresh optimism into England fans' hopes for Brazil.
The young players within the 23 will gain experience looking ahead to Euro 2016 - a tournament where England stand a much better chance of doing well - but Hodgson has warned they will be expected to make an impact at the World Cup too.
"Euro 2016 is in the back of my mind, but not in the forefront," he said.
"If there are young players in the squad it will be because they can do a job now.
"It will then be a bonus in 2016 as they will be experienced and hopefully that will serve us in good stead, but I don't intend to put them in the squad because of 2016."
Hodgson's defensive selection looks pretty straightforward.
The former Fulham manager said in March that his four centre-backs for the World Cup would be Gary Cahill, Phil Jagielka, Phil Jones and Chris Smalling.
Only if Jones is deemed unfit due to a recent shoulder problem will Everton teenager John Stones or Cardiff's Steven Caulker be called up.
Kyle Walker looks set to miss out because of a pelvic problem which has kept him out for two months.
Tom Cleverley and Michael Carrick are in danger of missing out due to their poor seasons with Manchester United.
Daniel Sturridge, Rooney and Danny Welbeck look set to be Hodgson's three main strikers.
Hodgson is a fan of Lambert, who is fighting it out with West Ham's Andy Carroll for a fourth striker place.
Jermain Defoe is sweating on his inclusion after swapping Tottenham for Toronto in March.
Hart and Ben Foster are expected to be first and second-choice goalkeepers. John Ruddy, Fraser Forster and Jack Butland are vying for the third slot.
Hodgson will also name up to seven standby players, who will be drafted in should injuries occur in the warm-up camps in Portugal and Miami.