Despite O'Shea being an integral figure for much of the campaign to date, Poyet opted for Carlos Cuellar at centre-back alongside Wes Brown for the Premier League clash at White Hart Lane on Monday night - a decision which raised a few eyebrows before kick-off.
However, Poyet stated he felt he owed it to O'Shea give him the reasons for being left out of the team.
"Because of the type of person he is, and the type of professional he is, he deserved an explanation," Poyet told the Shields Gazette.
"I don't do that every week.
"Every time I make a change, I don't call the player to tell him, believe me.
"I've got no problem telling him if he wants to know, but I can't call a player in every time I make a change.
"But John deserved an explanation because of who he is, and how we need him."
Poyet insisted that the decision to relegate his captain to the bench was not in reaction to the home defeat to West Ham, and it was simply a matter of picking a team he felt suitable to compete at White Hart Lane.
"People think I woke up in the morning, had a dream and thought I'd change John, and replace him with Carlos Cuellar," Poyet added.
"But it's not like that. There are reasons, there are different games. It's not just a reaction.
"Then after the game, you realise whether you were right or wrong.
"I think Carlos did well, and was probably the best of the three defenders."