There was a 2007 article in the Mercury News on the subject, but I'm having trouble finding it in its entirety. Here's an excerpt from it that was posted in a forum at 49erswebzone:
Bill Walsh spent almost his entire 49ers career pressing the right buttons, but he did have at least one regret.
Walsh traded draft picks with the Chicago Bears, who used their 1981 second-round choice on a hard-hitting linebacker out of Baylor University.
That pick, Mike Singletary, became one of the greatest linebackers of all time.
Fortunately for the 49ers, Walsh and Singletary teamed up eventually. They developed a bond when Singletary decided to pursue a career in coaching.
”Bill Walsh was the first person I called,” he said.
Singletary, now in his second season as a 49ers assistant, said Walsh graciously tutored him on everything from SCHEMES to SCHEDULING to PSYCHOLOGY.
”There were times that I would fly out from Chicago, have dinner with Bill, then turn around and fly back home again,” Singletary said of his early forays into coaching. ”That�TMs how much I respected him.”
Singletary said working with Walsh was much more fun than working against him. His Bears teams matched wits with ”The Genius” in many big games during the 1980s.
So what was it like playing defense against a Walsh offense?
”Frustrating, nerve-racking,” Singletary said with a laugh. ”You knew somebody was always open. Not only that, but the execution was really unbelievable.”
He recalled seeing film of a young Joe Montana scanning for receivers with the tempo of a band leader �" 1, 2, 3 and 1, 2, 3 �" all while maintaining elegant footwork.
”Walsh�TMs offense was always smooth and very simplistic,” Singletary said. ”Maybe some of the gurus thought it was complicated, but I never thought that. Walsh understood the fundamentals.”
...And a new day will dawn for those who stand long.