Przybilla has never been known as a passer. Walton is the greatest passer for a center in history. His real talent was defense, but no one mentions that anymore. Anyway, Joel is not Walton, even Bill's last full season in 1985-86, when Walton was the best center on an NBA champion.
On the greatest Celtic team of all time, could Joel really keep up with a broken down Walton? Compare the hobbling Walton to a healthy Parish, per 36 minutes.
http://www.basketball-reference.com/play-index/tiny.cgi?id=w1Ivt
And Walton's stats were held down learning his teammates and coach. This was Parish's 6th season on the Celtics, but Walton's 1st.
Despite Walton's per minute stats being better, Parish's PER was a little higher in the regular season, proving that PER isn't really per minute. By the playoffs, Walton had learned the system and his PER easily beat Parish, despite fewer minutes.
As the chart shows, Przybilla is pretty bad at assists per 36 minutes. Sly, I think you meant that Joel will need to focus upon talents requiring less mobility, like passing.