Aidy Boothroyd has called the England Under-21s job "utterly impossible" and defended the Young Lions' selection policy.
England need to beat Croatia by two goals on Wednesday and hope Switzerland lose to Portugal to reach the Euro 2021 quarter-finals in the summer.
They have had just one shot on target – none from open play – in their opening defeats to Switzerland and Portugal in Group D.
Since being runners-up at the 2009 European Championship, England have qualified from the group just once – under Boothroyd in 2017.
Jude Bellingham, Mason Mount, Jadon Sancho, Phil Foden and Trent Alexander-Arnold could have all been included in the squad in Slovenia but Boothroyd insisted the senior team remains the priority.
He said: "I know the senior men's job has been called the impossible job but the Under-21s is the utterly impossible job. The reason is the amount of players who have to be produced for the senior team and we are expected to win.
"There's a reason why we haven't won this for 37 years and why we haven't progressed as much as we thought we would, because our primary aim is to get players through to Gareth (Southgate).
"Could you imagine a reserve-team manager knocking on the door of a senior manager at a club and saying 'listen boss, I think today you should let me have the best player to win the reserve championship'. That just wouldn't happen.
"The only team that needs to win is the senior team. Everywhere else, winning is part of it, drawing is part of it and having adversity is part of it.
"The reason I say that it is the utterly impossible job is because new players come in, younger players come in and the wheel starts again.
"My job isn't to say to Gareth we should have Jude, Phil or Mason, it is about the senior team and it always will be.
"If someone is doing this job and hiding players and not allowing them to go forward then the system is flawed. I don't want to be the whinge bag to defend myself. They are facts but they are what the job is."
Callum Hudson-Odoi missed Sunday's tame 2-0 loss to Portugal and has returned to Chelsea with a shoulder injury while Emile Smith Rowe is doubtful.
Chelsea midfielder Conor Gallagher, on loan at West Brom, will start in Slovenia.
Boothroyd added: "We have a couple of players we are waiting to hear on, we are giving everyone the longest time we can.
"We have one or two bumps and bruises. I'm going to use the squad and I've got some good players who haven't played yet."
