The Steelers are still searching for their first win of the NFL season having fallen to 0-4 with a 34-27 defeat at the hands of the Minnesota Vikings at Wembley on Sunday.
"It's affecting the outcome of football games so obviously there's a level of concern regarding it. But it's fundamental, It's not anything mystical," Tomlin told reporters. "We miss a tackle, we miss a tackle. You have an opportunity for a big play, you have to tackle better. It's fundamental.
"That's how all losses are. Whether you're 0-4 or 12-4, usually those losses come down to a certain number of plays and the reality is you don't know when those plays are going to occur.
"So you have to be good fundamentally and be sound top to bottom and minimize the potential for explosion plays and doing things in great detail, fundamentals, lessen that."
This season is the first time that the Steelers have failed to win any of their opening four games since 1968.