Gareth Southgate takes charge of his first match since taking the England job full time insisting he is willing to instigate more “challenging conversations and difficult decisions” to put together a side capable of ending the cycle of national team disappointment.

Once described as too gentlemanly for top-level management, Southgate has already accelerated the phasing out of Wayne Rooney’s international career and telephoned Theo Walcott last week to tell one of the Premier League’s leading English scorers he was being left out because his England performances had not been up to scratch.

England take on Germany in Dortmund on Wednesday in Southgate’s first game since signing a four-year contract and the new manager used the occasion to argue the case it was still realistic, despite his own criticisms of the team’s tournament results, to aspire to be “the best in the world”.

Southgate made exactly that point during a meeting with his players on Monday, telling them they needed to be realistic about their shortcomings but maintaining that England still had enough talented players to think positively about winning the World Cup. “That has to be the ultimate aim because then that drives your behaviour,” he explained. “I think that is crucial because that is the mind-set we need to win.

“The tournaments haven’t gone so well recently. I’m part of that – I’ve been involved in tournaments as a player, so it’s not all down to these guys. But we can learn from these things and improve. We have to think differently and work differently. I’m trying to open their eyes to what we believe is possible. It will be a lot of hard work and it might need some more challenging conversations and difficult decisions on my part but that is why we are in elite sport.”

Southgate is expected to bring Marcus Rashford into the starting XI because of a minor injury that stopped Raheem Sterling from training before the team flew to Germany. However, Southgate was also given an early taste of the kind of misfortune that regularly seems to befall England when Phil Jones was injured on the eve of the match in a training-ground collision with his Manchester United team-mate Chris Smalling. Jones, whose propensity for banging into opponents has previously split open Wayne Rooney’s head and recently caused the same player a knee injury, suffered a suspected broken toe and has been sent for x-rays to determine how long he will be missing. The setback is potentially worse for United than England bearing in mind the congested fixture schedule at Old Trafford, with nine games for José Mourinho’s team in April.

Almost a year to the day since a 3-2 win in Berlin that provided plenty of false hope for Roy Hodgson’s team before Euro 2016, Germany are without the injured Manuel Neuer, with Marc-André ter Stegen stepping up as understudy. Mesut Özil and Julian Draxler are also unavailable through injury, though Southgate’s team are likely to come up against Manchester City’s Leroy Sané. Timo Werner, the 21-year-old RB Leipzig striker, might start for the first time in a game that will have Germany’s third most-capped player of all time, Lukas Podolski, captaining the side on the occasion of his 130th and final appearance.

Southgate is aware England’s followers have grown weary of promises from a succession of managers but hopes that a decent performance against the world champions will lift some of that scepticism.

“They will judge us on the performance,” he said. “They want an England team that is proud to wear the shirt – a team that is playing with calculated aggression and positive about what they do. We have to be tactically savvy because that’s an area of the game where we have to be at the top end if we want to succeed. And we have to be adaptable. The game is constantly evolving, with different problems at different times, and as a player now you have to be able to adapt very quickly.”

Of Rashford, Southgate said: “I thought he was excellent in the game against Chelsea last week. He makes powerful runs behind defenders and you can ask Gary Cahill how much of a problem that is. I liked his mentality when we had him for 10 days with the Under-21s. His mentality was very mature, very humble. He wants to learn, wants to improve, has a good view on the game and for a young player I think he has intelligent input when you ask him tactical things. He is not afraid to voice that, even among older players.”