Cork Gaines explains what Shane Battier meant by that statement after game 7:

When Shane Battier was struggling to make shots, he knew that he wasn't suddenly a bad shooter. He knew that eventually things would even out and his shots would start falling.

And he explained that perfectly when he told the media after game seven that "my mantra was I will regress to the mean."

"Regression towards the mean" is a concept strongly embraced by those in the advanced sports stats community that says extreme results don't tend to last. It is also apparently embraced by Battier.

For sports traditionalists, the idea of "regression towards the mean" is bothersome because it suggests that great performances or really bad performances aren't necessarily real. Instead, extreme performances are really just the result of an athlete fluctuating around an average and sometimes that fluctuation is greater than others.