Mike Shanahan never coached under Bill Walsh. But through three seasons on the San Francisco 49ers’ coaching staff under former Walsh lieutenant George Seifert, he absorbed everything he could about Walsh’s football philosophy and his teachings to players and coaches during a wildly successful 10-year run on the San Francisco sideline.

“Being part of San Francisco and going in there and studying tapes of his meetings for 10 years and being a part of that organization, I feel that I am a part of it,” Shanahan said, “because I took a lot of pieces from that offense and utilized them in our system.”

The quick passes, the zone blocking, the use of creative and ever-changing formations … those are key tenets of Broncos offensive football in the last 12 years, and many of them found their genesis in Walsh’s ground-breaking offensive scheme. His innovations were so revolutionary that they changed the way the game is played. You can scarcely turn on a football game on either the pro or college level and not see the perpetual harvest of Walsh’s fertile mind.