Wayne Rooney's eagerness to make a positive impact at the World Cup in Brazil has prompted him to take two fitness trainers to Portugal this week to ensure he is fully recovered from a groin complaint by the time England begin their training camp in the Algarve next Monday.

The Manchester United forward, who missed his club's last three games of the domestic season with the injury as well as a stomach bug, was named in Roy Hodgson's 23-man squad on Monday. The selection appears bold and progressive, with only 11 survivors from Euro 2012 and six who have played at a previous World Cup, with places for the relative international newcomers Raheem Sterling, Ross Barkley and the Southampton trio of Adam Lallana, Luke Shaw and Rickie Lambert.

The only slight fitness doubt that remains is Phil Jones, who has a damaged shoulder. Everton's John Stones and the Liverpool full-back Jon Flanagan are the only two of the seven stand-by players who will travel with the full squad to Vale do Lobo for a five-day training camp when the squad assembles after having this week off to relax. Rooney flew out for his break in Portugal on Monday with two fitness trainers, hired at the 28-year-old's expense, as he bids to be in peak condition ahead of the finals.

"He's going with two trainers, and [United's head of fitness] Tony Strudwick has been in touch with us wanting to know about the pitch in Vale do Lobo," Hodgson said. "This is a free week, a week where players go off and many do go to Portugal, where they have homes. Wayne is going on holiday there and he's not alone. A few of them are going out to Portugal. If they've got houses out there, that's where they go on their week off. I'm more than happy for the players to forget football for a week and get mentally prepared for the weeks ahead.

"But Wayne is so determined to be up and running when we get there on the 19th of May that he's going to continue his programme so he'll be able to join in straight away. His attitude is he's desperate to be up and running on the 19th May [when the squad travel to their base in Vale do Lobo]. I'm not as desperate for him to be fully fit on the 19th – I'm thinking more about the Italy game on 14 June – but it's still quite laudable that that's the way he's thinking and I'm not trying to dissuade him. But if I do get there on the 19th and the fitness people say he needs two or three days, I won't be shedding any tears."

Rooney still has much to prove at the World Cup, having failed to score in Germany in 2006 and South Africa four years later, his preparations for both having been severely disrupted. The striker had suffered a fractured metatarsal at Stamford Bridge towards the end of the 2005-06 season and was short of match fitness during a tournament that ended with a red card in the defeat on penalties by Portugal. He injured an ankle in the run-in to a prolific domestic campaign four years later and his performances in the finals were subdued and personal issues occupying his mind.

He had chosen to visit Las Vegas before Euro 2012, where he was suspended for the first two group games, and, despite scoring in the third to secure England's progress, looked sluggish as the team departed at the knockout phase.

"But the attitude and the desire are there," said Hodgson, who will attend Italy's friendly against the Republic of Ireland at Craven Cottage on 31 May to scout England's first Group D opponents in the flesh. "It's not right to put the hopes of the nation on the shoulders of one man. The four forwards we've selected are very good. I'm hoping the responsibility for scoring England's goals is shared and that might give Wayne the chance to show the other aspects of his game. Has he got the ability? Yes, he has. Let's hope he can show the form that makes Wayne Rooney the player he is." The England manager praised the impact made by Sterling, Barkley and Jordan Henderson over the course of the domestic season, suggesting the youngsters had "imposed their ability on my thinking". He had paid his latest visit to St Mary's on Sunday to watch Lallana and Shaw, who are the subject of bids from Liverpool and United.

Yet Hodgson has stressed he will demand his players are focused solely on England and the finals ahead in the build-up to Brazil, with agents discouraged from visiting their clients in Vale do Lobo, Miami or Rio de Janeiro.

"I have made it clear to them already, and they are perfectly happy with it: England is England and your club is your club," he said. "The two are not married together. I don't try, as England manager, to have any effect on you and your club and what you do at your club. On the other hand, you must accept when you come here it is us that matter, so a medical will have to be done outside of England time. They can do it in their spare time, say on a free afternoon, but we are definitely not going to have agents swirling around or a situation where a player has to leave the camp.

"I chose this squad because I really believe it's right for this moment. Time could prove me wrong. Circumstances can prove me wrong and results can certainly prove me wrong but I feel comfortable because a lot of thought has gone into this squad.

"We have agonised over certain decisions, Ashley Cole or Luke Shaw being the obvious one, but we've made our final decision in good faith. We believe it's a good squad. We believe in the players. I'll allow other people to decide whether it was bold enough."