Walcott famously earned a place in Sven-Goran Eriksson's 23-man party for the 2006 tournament in Germany, despite not having played a first-team game for Arsenal following a January transfer from Southampton.
As the clock begins to tick down towards Capello's date with destiny in South Africa next summer, Capello has not totally rejected the idea of picking a player who has never previously featured in the 20 England squads he has selected so far. "Yes. It is possible," he said.
"It would have to be a young player because I know the older ones better. We have four good young players already: James Milner, Aaron Lennon, Gabriel Agbonlahor and Theo Walcott. They can all improve even more this season."
When a couple of names were thrown at him, Arsenal's Kieran Gibbs received a positive response, although "he has to play". But Everton's Jack Rodwell was greeted with stony, non-plussed silence.
Gibbs apart, it is difficult to see Capello looking outside a core of 35 names, 16 of which he already has in his head as players he has plans to take.
The remaining seven will be decided on form grounds much nearer the time, which is why Peter Crouch cannot rest on his laurels despite his Wembley double.
"More or less," said Capello, when asked whether 16 players were virtually booked on the flight. "But I have to repeat the same thing every time. The door is open for all the players.
"We have to wait until April to see what the situation is with the players.
"I have spoken with some players who are injured like (Stewart) Downing and (Owen) Hargreaves. But I need to wait for all the players."