Wayne Rooney can be one of the stars of the World Cup, according to Ryan Giggs, who believes the forward can emulate his impact on Euro 2004.

Then the Liverpudlian was 18 and took the championships by storm, scoring four goals before injury in England's quarter-final with Portugal ended his participation as Sven-Göran Eriksson's side were eliminated on penalties.

Since then Rooney has had disappointing tournaments. Entering the 2006 and 2010 World Cups the forward was not match fit due to injury, while he missed the opening two matches of Euro 2012 due to suspension. England missed Euro 2008.

While Rooney is absent for Manchester United's final game, Sunday's trip to Southampton, due to a minor groin strain, Giggs believes the rest can benefit him. With Rooney now 28, the World Cup constitutes a last chance to shine at a major competition in his prime.

"I don't want to talk too much about England but the young players they have at their disposal is for English fans really exciting and that can only help Wayne," said the interim manager. "You have seen the emergence of [Raheem] Sterling, [Adam] Lallana, [Daniel] Sturridge, obviously Daniel [Welbeck] here. He has young vibrant players around him and that can only help."

Giggs is clear that Rooney can shake up the World Cup as he did at Euro 2004. "He will be going into it relatively fresh," he said. "The injury has probably done him a favour. I know he is excited, just like all the lads who are going to the World Cup. They can't wait and rightly so because it is a great experience for them. Wayne is a top player and I think he is at a good age – at the peak of his powers. I know for a fact he cannot wait for it.

"The injury was just a little groin strain. He is fine. He has done all the work in the gym. He trained yesterday. He will be fine. He is going away next week and working on his fitness as well, so it has probably helped him."

Giggs also says that, at 19, Adnan Januzaj should join Belgium's party in Brazil. "The experience of a World Cup is something you would never take away from a young player and Adnan is the kind of player who could light up a World Cup whether it is coming off the bench or starting games," he said. "He just floats with the ball effortlessly. He is one of those players you just love watching."

Giggs's own future is to be decided in the close season. While Louis van Gaal, the prospective new manager, will offer him a senior coaching role when appointed, the 40-year-old admits it will be difficult to retire as a footballer whenever that day arrives because he still "loves" playing.

Regarding how this decision will be taken, Giggs said: "Does the new manager want me? Do I want to put my body through another year? Eating the right things, the discipline [of another pre-season]. Do you want to go out still enjoying it and not go out a year too long? These are all things I have got to consider.

"It will be difficult to stop playing. It is easier probably when you have had injury problems. I have seen players who just can't go on and they are not training and just going out for games. I have never really had those problems. I have got to weigh up a lot of things."

He is clear, though, that he would like a future in management. "I have enjoyed the whole experience," he said. "You get a satisfaction when everything goes right, although when you lose you are angry and disappointed. But it has definitely helped me prepare for what will come after my playing career."