Van Gaal hauled Van Persie off 15 minutes from the end of Sunday night's dramatic 2-1 win over Mexico and watched as his replacement Klaas-Jan Huntelaar set up one goal and score the winner from the penalty spot.
"The substitution of Van Persie was tactical.
"Let's not forget before he joined team he was recovering from an injury. It's difficult for him to keep up 90 minutes especially in these conditions.
"Anyway, this trainer wants to win. So he makes the changes and the substitutions he needs. It's simple. Nothing else matters."
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