Professional skills have long been perceived as lacking in junior engineers. Adopting a social realist theoretical framework of knowledge in practice, a hypothesis-based survey study of early career engineers' perceptions of engineering expertise was conducted. It investigated a professional skills readiness difference between initial career trajectories (hypothesis 1) through an analysis of engineering expertise perception, and whether this difference decreases over time as engineers mature (hypothesis 2). Both hypotheses were supported by three statistical tests which established the specific nature and size of this difference. Three themes were identified: "Academic bias," "Technical competence bias," and "Rationality bias." Thematic analysis through the framework of these three themes indicates how context and complexity ("Semantic dimension") and Knowledge and Knower ("Specialisation dimension") were understood in practice. The three themes expressed challenges over these two dimensions in understanding "Technical knowledge," "Collaboration," and the "Legitimate basis for practice," leading to recommendations for education and practice.