Gareth Southgate's team will go through a final training session on Sunday morning before flying to Volgograd, where they hope they can make a winning start in Group G.
Among those facing anxious waits are Eric Dier and Jordan Henderson, both jostling to be England's chief destroyer in midfield, while Ashley Young or Danny Rose could play at left-back.
"We have an idea of the team now," Manchester City's Delph said on Saturday. We've worked on various systems with different personnel. The team is not guaranteed to be the X1 players we think it might be, there might be changes. But from the set-up we've done, it's pretty clear to see who is probably going to be starting."
Some coaches prefer to keep players guessing, the theory being that uncertainty ensures training sessions stay sharp while nerves have less time to settle.
"I think for certain players they like to know," Delph said.
"But whether you are selected on the day of the game or the day before I think it is all the same thing. As long as your mindset is clear, you know what you need to do."
Delph is unlikely to be among the starters against Tunisia and he may not even be in the country given the 28-year-old has vowed to return to England if he is called back for the birth of his third child.
His wife, Natalie, is due on June 30, two days after England play Belgium in their last group game in Kaliningrad.
"It's very exciting if I'm being honest," Delph said. "It's been a fantastic year for me on a personal level and to be expecting our third child is absolutely amazing. I'm waiting on the text to say 'get back home'."
Southgate's players watched the six-goal thriller between Spain and Portugal on Friday night as each side showed why many have them circled among the favourites in Russia.
England have managed only six knock-out wins at major tournaments since being crowned world champions in 1966, but Delph believes this group can match even the most formidable opponents.
"We've got that calibre of player in our squad – very exciting, very fast, loads of athleticism, fearless, young players – so I think we've got that extra gear," Delph said.
"The Premier League is probably the best league in the world and for a lot of our players, the peformances they've reached this season have been phenomenal."