The 31-year-old Defoe did not make England's main 23-man squad which features Wayne Rooney, Daniel Sturridge, Danny Welbeck and Rickie Lambert at forward. Instead the Major League Soccer star was one of two strikers named to England's seven-man standby list.
The first-team England strike force has a combined for 51 international goals and 124 caps in Rooney (38 goals, 89 caps), Sturridge (3, 10), Welbeck (8, 21) and Lambert (2, 4).
Manager Roy Hodgson also has attacking options in midfield in Alex Oxlade-Chamberlain, Adam Lallana, Ross Barkley and Raheem Stirling, among others.
"Certainly once you move into that front six position, I think we have a lot of options. I think there's a lot of possibilities," Hodgson told a news conference Monday in London. "A lot of players can play in different positions. And I'd like to think that's that a very exciting group we have for those front six positions."
Defoe, a veteran of the 2010 World Cup who has 19 goals and 55 caps with England, had figured in all but two of Hogson's matchday squads before this.
But Defoe, who has three goals in four MLS games, may not have been helped by playing overseas.
According to Opta Sports, only four of the 114 players chosen for England's last five World Cup squads played for non-English teams (Calgary-born Owen Hargreaves twice, David Beckham and Fraser Forster).
Hargreaves played for German's Bayern Munich, Beckham for the Los Angeles Galaxy of MLS and Fraser for Glasgow Celtic.
"Jermain Defoe's international career could be over," the Daily Telegraph said after the squad announcement.
Veteran fullback Ashley Cole, a 33-year-old fullback with 107 caps, announced his international retirement Sunday. Hodgson had opted for veteran Leighton Baines and 18-year-old Luke Shaw over Cole.
Monday was the deadline for teams to provide FIFA with their 30-man provisional squads. The final 23-man squads must be declared by June 2.
Injuries could still change the face of the England squad with Defoe and West Ham's Andy Carroll selected as cover for up front.
The full squad heads to Portugal next week to begin World Cup preparations, before playing Peru at Wembley on May 30.
There was no immediate word from Toronto FC on how much time Defoe might away spend with England.
Toronto manager Ryan Nelsen, who captained New Zealand at the 2010 World Cup, has been torn about Defoe and the World Cup. While backing his player's skills on the international stage, he also wants his top striker wearing a Toronto jersey as often as possible.
"If I was the England manager, I probably would pick him," Nelsen said last week. "Because you know what you're going to get with him — you absolutely know what you're going to get with him.''
Defoe offers experience and a scoring touch off the bench. He has scored everywhere he has played.
Hodgson opted for youth in most cases although he went with the 32-year-old Lambert up front. Rooney is 28, Sturridge 24 and Welbeck 23. Lambert, a late bloomer on the international scene, has two goals and four caps.
The average age of the England's squad is 26 years 117 days, more than two years younger than 2010 but older than 2006 (25 years 258 days), according to Opta.
Barkley, Sterling, Luke Shaw and Jordan Henderson have a combined 14 caps. Eleven of the 23 players have 10 caps or under while only six have been to a World Cup.
"Bags of attacking talent, much unproven but exciting nevertheless, blatantly short defensively through the centre," tweeted former England striker and current TV pundit Gary Lineker.
The greybeads on the squad are Frank Lampard (35), captain Steven Gerrard (33) Phil Jagielka (31), Lambert (32) and Ben Foster (31).
Youngsters include Sterling (19), Oxlade-Chamberlain (20), Henderson (23), Phil Jones (22), and Jack Wilshere (22).
After the Portugal camp, England flies to Miami for warmup games against Honduras and Ecuador before opening the World Cup on June 14 against Italy.
England is in a group with Costa Rica, Italy and Uruguay at the summer tournament in Brazil.
Toronto will be losing Brazil goalie Julio Cesar and U.S. midfielder Michael Bradley to the soccer showcase.
The England standby list also includes uncapped defenders John Stones (19) of Everton and Jon Flanagan of Liverpool, less than a year after featuring for England in the U20s World Cup in Turkey last summer.
Flanagan is the nephew of Toronto FC defender Bradley Orr.
The other standby players are Norwich goalkeeper John Ruddy and midfielders Michael Carrick and Tom Cleverley of Manchester United.
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