Karpov has an even record against Petrosian and we all know what Fischer did to Petrosian . Those who think Fischer feared Karpov know little of chess .
Petrosian is not a good example to measure Karpov's strength at that time. Spassky would be a better one, as he played matches against both Fischer and Karpov.
Fischer beated Spassky +7-2=11 in 1972, and Karpov beated Spassky +4-1=6 in 1974. I can not see any confidence from Fischer. It would be a tight match. However, if it was a unlimted match as Karpov-Kasparov 1984-1985, Karpov would physically collapse after 40 games.
The problem with this comparison is that we can never be sure that Spassky wasnt ordered to lose to Karpov in their match . Karpov , the good commie , was the new darling of soviet chess and they certainly didnt want to see Spassky play Fischer again so Spassky may very well have been pressured into not playing his best against Karpov .
He could have more than the world #1 like the world's greatest #1 (in temrs of years).