London: Gareth Southgate will begin the process of fine-tuning his World Cup starting line-up when England host Nigeria in Saturday's friendly at Wembley.
Southgate has just two more opportunities to see his team in action before they jet off to Russia for the World Cup.
Saturday's clash with Nigeria is followed by a second friendly against Costa Rica at Elland Road next Thursday.
Both of England's opponents have qualified for the World Cup and their differing styles will offer Southgate a glimpse at how his players will cope with the varied approaches they will face in Russia.
But the England manager's main goal will be to experiment with his line-up to learn as much as possible about the players he expects to feature in their first group match against Tunisia in Volgograd on June 18.
Top of his to-do list will be resolving which of his inexperienced goalkeepers is his first choice.
Stoke's Jack Butland, Everton's Jordan Pickford and Burnley's Nick Pope have only nine caps between them.
Pope had a brilliant season for Burnley and kept more clean sheets than any other English keeper.
But he has yet to feature for England, making Butland -- who has seven caps -- the slight favourite at this stage.
Southgate is expected to play a three-man defence, having used the system in recent matches.
Kyle Walker is set to start on the right of the back three, with his Manchester City team-mate John Stones in the middle.
That leaves Chelsea captain Gary Cahill and Leicester's Harry Maguire likely to fight for the other spot.
If Maguire starts it would complete a remarkable rise for a 25-year-old who travelled with his brothers to watch England as a fan at Euro 2016.
"It was a great occasion for myself to go over there and see them play live and the atmosphere," Maguire said.
If Southgate plays Walker in central defence, he still has plenty of options at wing-back.
Kieran Trippier and Trent Alexander-Arnold are the contenders on the right and Danny Rose and Ashley Young on the left.
With Tottenham striker Harry Kane certain to start after being named England captain, Southgate will choose between Jesse Lingard, Raheem Sterling and Dele Alli for the two attacking midfield roles.
England, who also face Panama and Belgium in Group G, qualified for the World Cup with ease, winning eight of their 10 matches to finish as unbeaten group winners.
But Slovakia, Scotland, Slovenia and Lithuania hardly posed a serious threat to England and Southgate, who took over from Sam Allardyce early in the campaign, knows the acid test of his ability -- still in question for some -- will come in Russia.