The 18-year-old struggled at Fratton Park, with Pompey losing the League One clash 2-1.
"Miguel is such a young player who is finding his way in professional football," he said, as reported by The News.
"It was a tough start but this is the life of a professional footballer – it's not always easy.
"But he's a top player and he will learn a lot from today.
"And like I said, for us, we didn't get the team right – we accept that, have to take responsibility for that."
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