Jack Wilshere has offered the frank admission that “time is running out” for him to make his mark both at Arsenal and in the England side, with the midfielder conceding he must maintain form and fitness in the campaign ahead if he is finally to fulfil his considerable potential.

The Londoner’s career has been stop-start over recent seasons courtesy of a series of untimely injuries, most notably to his ankles but also, back in March, a hairline fracture of his left foot sustained in England’s friendly against Denmark. Wilshere has started only two games since then, his country’s friendly against Ecuador in Miami and Tuesday’s final group game against Costa Rica in Belo Horizonte, with the midfielder’s frustration clear.

He returned home with Roy Hodgson’s crestfallen squad on Wednesday determined to prove his worth next term and justify the rave reviews that saw him first capped at 18 in the aftermath of the 2010 World Cup. Yet, while much has been made of the youthful quality of the current England squad, Wilshere is unconvinced he qualifies as a player of promise any more. “It’s easy for me to stand here and say: ‘We’re young, we can go forward,’” he said. “But if you look at Germany, a team like that, they’ve got young players who are delivering now.

“Time is running out for us to say we’re young any more. I’m 22. Ross [Barkley], Luke [Shaw] and Raheem [Sterling] are young players. They showed in the tournament what they can do. But in the next tournament, we really have to deliver. I think it is [a big year for me]. I’m not young any more. I’m going to be 23 in January and that’s a good age for a footballer. It’s a big season for me, it’s a big season for Arsenal. But at the moment, I’m devastated. I’ve got to try and get over this and then try to move on next season.”

German midfielder Mesut Özil says the England's early exit from the World Cup was because they didn't put 100% effort into their matches Guardian

Wilshere’s cameos in Brazil offered only flashes of his quality, most obviously when he operated in a three-man midfield against Costa Rica in tandem with Barkley and Frank Lampard. That match had seen the Evertonian and Shaw handed their first competitive starts – albeit in a dead rubber as far as the group was concerned – with both impressing. “I think it went all right,” said the Arsenal midfielder. “It wasn’t about me, it was about the team. In a game that doesn’t matter, it can be tough, it can be difficult, but I think we showed good things in patches. Going forward, we’ve got some good young players.

“Luke Shaw looked like he had played over 100 games for his country. He was just a natural. So there were some positives to take. It is a nice group of young players and hopefully we can stick together, learn from this tournament, take all this disappointment and bottle it up. This is the worst feeling. I won the FA Cup at the end of last season so I know what it’s like [to win something]. I was fresh from winning, so to then have this disappointment is not nice. We’ve got to bottle this feeling up and take it on.

“But what excuses are we going to use? We prepared well. We’re just disappointed. It’s all a bit raw. When we get back to England then we’ll wake up every day and think: ‘What if this? What if that?’ We’ll watch the three games over, see the positives we can take and try to get the negatives out of our game. As for me, pre-season is not far away. I’m going to have maybe a couple of weeks off, but I don’t want to lose my fitness.

“I’m going to carry on training, do my bit, because I only played two games in the last three or four months. I will go back [to Arsenal] early. They are going away [to New York] and I’m not sure I’m going on that, but I will definitely still do my little bit. My fitness is on the way up and I don’t want to lose that.”

England’s qualification campaign for Euro 2016 begins in earnest in the autumn with a friendly against Norway at Wembley on 3 September, five days before an awkward trip to Switzerland for the first competitive fixture of the campaign. Hodgson may still be waiting on his captain, Steven Gerrard, determining whether he will continue to play at this level but the manager intends to continue to lean on the clutch of younger players who have emerged over the past few months.

That will have implications on the future international careers of Phil Jagielka and Leighton Baines with the latter now under pressure from Shaw for a place in the side. “There’s not just Leighton but the likes of Kieran Gibbs and Danny Rose,” said the teenage defender, whose start in Belo Horizonte had come just 561 days since his full debut at Southampton. “You can’t say it is between me and Leighton Baines because it is not. We will just have to see, but I will keep pushing myself and show people what I can do.

“I’ve learned a lot over the last five weeks, training with world-class players who have played in the Champions League. There have been glimpses of the youngsters coming through, and there is a very bright future for England. Playing regularly in the best league in the world for Southampton has benefited me, just as it has for Raheem and Ross to have played at Liverpool and Everton. So why can’t other clubs do that?”