Corry Evans and Alex Pritchard both dropped to the bench for the game, and their absence had an obvious impact as the Black Cats struggled throughout the first half.
The pair helped Mowbray’s side gain some control late in the game but by then Ellis Simms had been substituted as he tries to build up to full fitness, and Cardiff were able to hold on for the win.
Sunderland are still yet to win back-to-back games since returning to the Championship.
“They had control of the first 20 minutes but we managed to break away a couple of times and have some really good chances,” Mowbray said.
“It felt as if after 20 minutes it could easily have been 2-2. We made a few changes to try and freshen the team up and ultimately I don’t think it helped the team.
“We’re disappointed, we wanted to follow up a good win and get back-to-back wins. You’d have to say Cardiff played well, we lacked the intensity to stop their passing and their movement in the first half.
“We have to keep persevering, we’re trying to integrate some young players into our team. We did get much better when we got experienced players on and had some control, but we couldn’t find the goal.
“I was fearing getting injuries because of fatigue, which is why I made the changes.
“Every day we assess these players on where they are, their muscle fatigue and you have red, amber and green. We have a lot of players in red, a lot of players who are in danger of breaking down. That’s not me, that’s a scientific assessment of how they are.
“You then have to pick a team and you know you need to change it, because you know they are going to be tired and jaded. If you pick them and you go and get beat or they get injured, you beat yourself up.
“And to be fair, that’s why you have squads, you have to trust your players. At the moment, we’re going through a process of getting to a point where you can trust them all.”
Mowbray said he opted against making half-time changes as he thought the opportunity to speak closely to his players could help fix their issues without making substitutions.
“I don’t think so, you have to give people an opportunity,” Mowbray said.
“You tinker with things and at half time you have a better chance of fixing what has gone wrong. It’s not easy when you’ve got a lad 60 yards away from you in a loud stadium and English isn’t their first language.
“We had the chance to speak to them, to show them what we needed to fix. We were better second half though we lost an early goal, and maybe they went into defensive mode as well to be fair, but we finished on top.”