The 18-year-old sensation has forced his way into the United team in recent weeks, scoring his first goal for the club against Real Sociedad and coming off the bench to provide two assists in the Carabao Cup win over Aston Villa on Thursday night.
Argentina boss Lionel Scaloni has included Garnacho in his extended squad, which is set to be reduced to a final 26 on Sunday.
While the youngster is not expected to make the squad for Qatar, his recent form could inspire a late surge although ten Hag has suggested this winter’s competition would come too soon for him.
‘It’s difficult to say,’ Ten Hag said of Garnacho’s World Cup prospects in the post-match press conference. ‘I don’t know all the available Argentina players, of course I know a lot of players from Argentina, what is available for them from 26.
‘And the other thing is it’s a big step to go to a World Cup, where the best players in the world come together, it’s a big step.
‘I don’t know if that’s the right step for him. I think he has to keep his head clean, stay calm, work hard and develop, I think go from game to game.’
After a drab goalless first-half, United fell behind through Ollie Watkins’ goal but immediately responded through Anthony Martial’s equaliser.
United fell behind again after an own goal from Diogo Dalot but Marcus Rashford pulled his side level six minutes later with a fine effort.
Bruno Fernandes’ deflected effort put them ahead with Scott McTominay latching onto Garnacho’s superb ball to seal the win.
‘I think we made good steps in the last months with our mentality and this is further evidence of it but we are not there, where we want to be,’ ten Hag said.
‘Sunday was really poor. It can’t happen. We have to blame ourselves for the performance. But what we see after such a performance on Sunday, to fight back today, even when twice down, is good and a real compliment for tonight.’
United take on Fulham at Craven Cottage on Sunday in their last game before the World Cup break.
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