Why second rates were not fallback warships

Age-of-sail second rates were purpose-built capability choices, while the Lord Nelson class better illustrates continuing a known design as insurance against a revolutionary successor.

Question

Were Slava-class cruisers analogous to second-rate ships of the line kept as spares?

Short answer

No. Second rates filled their own requirement; completing the Lord Nelson class alongside the revolutionary Dreadnought is a closer example of fallback procurement.

Notes

Second rates were built for a specific requirement rather than kept as inferior first rates. Their extra gun deck offered fewer advantages than the greater length available in a first rate, so they make a poor analogy for a deliberately retained backup. Age-of-sail construction offers no clean equivalent to that procurement strategy. Completing the Lord Nelson class after HMS Dreadnought had made it obsolete is closer: the Royal Navy preserved proven ships in case the revolutionary new type failed.