The Steelers led the NFL in most defensive categories from 2004 to 2012 but have struggled so far this season, culminating in Sunday's loss to the New England Patriots - a match that saw them concede the most points (55) and yards (610) in franchise history.
Safeties Troy Polamalu and Ryan Clark accepted some responsibility for the defeat after the match, but Tomlin believes that the duo are still capable of performing at the highest level despite their advancing years.
"That was a sub-standard performance, and I appreciate their willingness to accept responsibility for that," Tomlin told reporters.
"I share that. But at the same time, I've got a great deal of confidence in them and their abilities to play winning football for us.
"After really combing through the tape, there were really no blatant breaches of [effort]. I really feel like more than anything we were beaten. As humbling as it may seem, I think we can grow from this and move forward."
The Steelers have only managed two wins so far this season, leaving them bottom of the AFC North.