"I have had a couple of decades thinking it through", Southgate said when focus turned from the group stage to a last-16 knockout against Colombia in Moscow on Tuesday.
A minor thigh injury that he picked up in the opening match against Tunisia kept Alli out of the 6-1 win against Panama, and although he was probably fit enough to have played in the final Group G game against Belgium if needed, coach Gareth Southgate preferred not to risk him.
He added that it was "important we react positively to the defeat" against Belgium.
Striker Kane has been in prolific scoring form, netting 135 goals in all competitions for Tottenham over the last four seasons.
Sunday starts with Russian Federation hosting Spain in Moscow's main stadium, with the late game pitting Denmark, which hasn't lost since the fall of 2016, against Croatia, which eased through its group with three wins.
Southgate saw his tame effort saved and England crashed out in the semi-finals with a side under Terry Venables that were good enough to land the trophy themselves. "Whoever we play are capable of, on a one-off game, beating us".
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Tomorrow's match will decide on the victor of their Group A, which also enrolls the teams from Saudi Arabia and Egypt . More recently, the team finished fourth in South Africa in 2010 and made the round of 16 in Brazil four years ago.
There has been a penalty shootout at every World Cup since 1982 in Spain, and while it is still a matter of contention whether this is the best way to decide a victor, the post-match shootout is now common at all levels of the game.
It is a chance for the Three Lions to win a first knockout match since 2006 and atone for some galling major tournament defeats, the most high-profile of which was their humiliating Euro 2016 exit to minnows Iceland. "FA Cup ties went to two or three replays so we weren't in those situations as often as we are now".
"We want to win football matches, so we're not happy to come away from here having been beaten".
"But if we believe it's the right thing then stand by it". Your team's last-16 game with Colombia should be an absolute doddle.
Martinez went on to commend the preparation of the teams taking part in the tournament, singling it out as a reason for the high quality of football, which has already been marked out as making Russian Federation 2018 one of the most exciting World Cup of recent times.
Colombia finished top of Group H but Merson admits he's not been impressed with their performances.
He said: "I think both the teams were fairly evenly matched".