The youngster has been a shining light for the Saints in the Premier League so far this season.
Martin believes that him withdrawing from the England Under-19s was not a major concern.
He explained to Daily Echo: "Tyler stayed because he had a few knocks. He was nursing something before the Arsenal game. It keeps him fresh for us.
"He's fine. He had a week off his feet, had treatment and was rested. We also have to respect and appreciate that Tyler's life has changed quite dramatically in the last few weeks.
"Not just physically but mentally, the spotlight he is under, the praise he's getting and all the interest.
"We have to take in the mental fatigue as much as the physical load. He was carrying one or two things physically because the intensity stepped up for him.
"He's in a good place. He's had a good bit of rest and some treatment. He's dipped in and out of training this week. He will be ready."