The Dutch forward played the full 90 minutes this afternoon as the Red Devils lost 1-0 at home to Newcastle United.
Moyes's plan was to substitute Van Persie after an hour, but, with his side trailing, the Scot kept the striker on the field.
"I was due to take him off after 60 minutes, but if I had people would have said 'what are you doing?' We were chasing the game and needed to get a goal back," Moyes told reporters.
"You try and win the next game. We move on. We will try and win the next game, never think much further than that."
Wayne Rooney missed the game through suspension.