Jack Ross has told Reece James to make the most of his opportunity after revealing that Bryan Oviedo has apologised for his red card.
Oviedo saw red on Tuesday night after kicking out at Peterborough United forward Marcus Maddison.
The red significantly curtailed Sunderland's progress in the game as they dropped two points at the Stadium of Light.
Ross says Oviedo is still 'genuinely gutted'.
"He came to speak to me this morning, he was very apologetic," he said.
"He was gutted about it, it is the first red card of his career. I said after the game that it was uncharacteristic.
"For me, it's a mistake, a poor choice. A mistake like passing it back to Jon, someone intercepting and scoring. It's a mistake. The game is played by human beings, it was disappointing but he is genuinely gutted, I can see that in him.
"It's happened, there's zero Bryan or I can do about it now.
"He'll miss a few games and then it'll be up to him to get back into the team because it gives an opportunity to someone else now."
Oviedo's red, as well as a disappointing injury for 20-year-old Denver Hume, has opened the door for James.
The former Wigan full-back looked set to be first choice when he arrived in the summer bit opportunities have been few and far between.
Now, however, he has the chance to secure his place in the team with Oviedo set to miss the next four games and Hume absent for six weeks.
"I had a similar conversation with him this morning," Ross said.
"One, it shows you how strange the game can be and two, it is an opportunity.
"Not just a one off, but potentially a run of games. The thing with Reece is that's done fine when he's had opportunities. I go back to Gillingham away, he was thrown in without game time and did really well on the night.
"For me as a manager, it stresses how important it is to keep communicating with players when they're not in the team. Reece and I still speak, his attitude has been good and he has trained really well.
"You never know when you'll need players so I think the good thing is I'm not all of a sudden going on like his best pal when I haven't spoken to him for weeks.
"He's a good player, he's won promotions with Wigan. I've got no worries about him at all, I just hope he takes the opportunity and then it's up to someone else to get him out of the team.
"We're fortunate that all of the left-backs, if you replace one with another the style doesn't really change," Ross added.
"They're all similar, I suppose that could be a criticism and you could say you should have more variety, but it should help us in terms of the style of play."