Berger, bothered lately by strained hamstrings in both legs, averaged 41.9 yards on 42 punts but had punts of only 27, 32 and 35 yards Monday night in Washington.
Ernster joined the Steelers after punter Daniel Sepulveda was lost for the season with a knee injury on the first full day of training camp. Ernster averaged 41.7 yards on 80 punts for Denver in 2006.
The Steelers brought in Berger later in camp and kept him after he outpunted Ernster during the preseason.
The Steelers have now changed their punter and long snapper in the last 10 days. They signed Jared Retkofsky as their snapper after Greg Warren sustained a season-ending knee injury Oct. 26 against the New York Giants.