• Manager hails striker as ‘unbelievable’ but says he is building younger team • ‘When I took over we had six or seven players above 33. He’s already 34’

Louis van Gaal has called Zlatan Ibrahimovic’s performances this season “unbelievable” but has indicated he is reluctant to sign the forward for Manchester United because of the Swede’s age. Ibrahimovic is out of contract at Paris Saint-Germain in the summer and United are one of the Premier League clubs who have been monitoring the 34-year-old.

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The Guardian understands Van Gaal has not completely ruled out making an approach for the striker but, in an interview with the Swedish TV station Viasat, he pointed to the number of players over 30 who have left since he became manager in 2014 to allow him to rebuild United’s squad.

Asked what United required to become serious challengers for the title next season, Van Gaal said: “We need to improve our selection [squad], because when I took over we had six or seven players above 33 years old. Nobody knows that anymore because now they are gone. But now we have a much younger team and still we need a much younger selection because we need creative players in attack and also fast players.

“I like [our] own youth players more because they already know the culture in Manchester United, and that is also the philosophy for example of Ajax or Barcelona and also Bayern Munich.”

On Wednesday evening Ibrahimovic scored his 35th goal of the season for PSG in the 2-2 draw with Manchester City in the Champions League quarter-final opening leg, and Van Gaal said: “I think it is unbelievable what he is doing. I saw the game against Manchester City, and it was a big disappointment for me because he should have scored two times at least.

“Paris Saint-Germain is Zlatan and that is fantastic. When a manager like me, who favours the team [above the individual], is saying that, that is a compliment for him.”

Van Gaal refused to say if he could see Ibrahimovic at United next season. “You never know? I cannot say anything about that subject,” he said. But when the Dutchman was asked whether the player would fit into the Premier League, he replied: “He’s already 34 and I just spoke about the age [of the players] I let go [from United].”