Samuel Johnson, though an ardent supporter of Neoclassicism, embraced several romantic tendencies. His views on poetry, nature and imagination were similar to that of William Wordsworth and in this way marked the onset of a revolt against Neoclassicism.
In the Life of Milton, Johnson says,
Poetry is the art of uniting pleasure with truth, by calling imagination to the help of reason… 
…since the end of poetry is pleasure that cannot be unpoetical with which all are pleased… 
Johnson’s belief of composing poetry for pleasure, in these lines, is profoundly similar to Wordsworth notion of poetry in Preface to Lyrical Ballads. Even Wordsworth believed that the sole purpose of poetry is to render pleasure in the mind of the reader.
We also find Johnson critiquing Milton’s description of natural settings in The Paradise Lost.
But his images and descriptions of the scenes or operations of Nature do not seem to be always copied from original form, nor have the freshness, raciness, and energy of immediate observation. He saw Nature, as Dryden expresses it, through the spectacle of books; and on most occasions calls learning to his assistance… 
Johnson’s comments undoubtedly comply Wordsworth’s view of Neoclassical poetry being a play of just form and structure, and devoid of passion and emotion. Moreover, Johnson’s views on need of moral purpose in a poetic composition as well as the definition of Imagination are strikingly similar to that of Wordsworth.
In fact, Dr. Samuel Johnson's work and ideas on poetry, nature etc. (and deviation from Neoclassicism) are known to be the precursors of Wordsworth's firm Romanticism.
In preface to Shakespeare, Johnson transcends his literary prejudices and negates the Aristotle’s Unity of trinity as a requisite for judging Shakespeare’s work. These views, too, mark a transition from his stern Neoclassical tendencies towards the Romantic revival. A major part of ‘the Age of Johnson’, for that matter, has evidences of deviations from stern Neoclassicism and a more accepting attitude towards Romanticism.