Put simply, basic pattern-matching has a defender playing zone through the first part of a route. Then, as the receiver makes a move to affect the stem of the route, the defender switches to man coverage.
ESPN analyst and former NFL defensive back Louis Riddick, who broke down two plays in Part 1 of “The Match Game,” played for Saban and head coach Bill Belichick in Cleveland in 1993 and 1994, and he was introduced to pattern-matching from the first day he hit the Browns facility. Saban and Belichick had already dialed it up by that time.
“Pattern-matching was always a part of what the safeties and cornerbacks did,” Riddick told me. “If we called it Cover-4 (four-deep, man-based coverage), there were very specific reads for us when routes got into that 10- to 12-yard area.
The coverage turned from zone to man. You ‘buy’ a route based on which way the receiver went — whether they broke to your left or your right, and where your help would be coming from.
It always started off as a zone call, but once they got into your specific area, the specific depth you needed them to get to, it quickly turned to man.___________________________________
This is talking about Belichick/Saban but it's the same concepts that Fangio developed and his guy Brandon Staley brought them to Rams and now Morris runs them. Rams (and those running system) "don't cover green grass" they don't drop to a spot... they look to see what the offensive concept is and then they know whose man is whose.
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ramsrule.com]
