“We aspire every year to be compared to one of the great defenses of all-time – the ’85 Bears, the 2000 Ravens, and the (1970’s Pittsburgh Steelers) ‘Steel Curtain,’ ” cornerback … CLICK HERE if you are having a problem viewing the video on a mobile deviceSANTA CLARA — Historically woeful on defense in recent years, the 49ers have reversed field. They’re dominating. They’re undefeated. They’re shooting for the stars.Which universe? A place among the best defenses in NFL history.