Amongst many Evangelicals today there seems too little an appreciation of Systematic Theology. You can easily imagine people saying, "Let's not talk about doctrine, I just teach the Bible" Granted, there is a big danger for our theologizing to be too speculative, or too much about what other people think, rather than a proper consideration of what God tells us as we consider the whole of the Scriptures. Nonetheless, as they say, we should not throw out the baby with the bathwater. In an essay I was reading by Phillip Jensen, he provides a helpful corrective for those who try to avoid doing Systematic Theology in relation to preaching. His words come under the heading of "Preaching God's Word Depends on Systematic Theology":
Again, because the Word of God is unitary, preaching God's Word will always display our systematic theology. Expository preaching is sometimes put in opposition to systematic theology. This is a sad mistake. Expository preaching in particular will reveal our competence or incompetence as systematic theologians.
The preacher who prides himself on being "a simple Bible man" does not understand himself. He may claim to just "preach the passage" in front of him without being bogged down by theology or doctrine or systems. yet he rarely preaches the passage in front of him. Rather, he will unconsciously preach the church tradition from which he comes. Or worse, he will preach his own hobbyhorses and ideas. For without a consciously self-aware and well-considered theology that is open to being framed, corrected, and developed by the text of Scripture, the preacher's own frame of reference will overwhelm the text. That frame of reference may be his church's tradition or maybe his own personal experience, but it will not be the Bible.
(This excerpt has been taken from "Preaching the Word Today" in Preach the Word: Essays on Expository Preaching in Honor of R. Kent Hughes, p.163.)