This article considers explicit knowledge and processes in second language (L2) learning from a usage-based theoretical perspective. It reports on the long-term development of a single instructed adult learner's use of two L2 constructions, the German Perfekt of "gehen" ("go," "walk") and "fahren" ("go by vehicle"), which was tracked over a period of more than 3 years. The results indicate that explicit knowledge and processes seemed to have a powerful impact on the participant's L2 learning and use, apparently enabling him to override the predicted bottom-up developmental path in certain circumstances and take a top-down approach instead. Specifically, it was found that the development of fahren was consistent with the predicted trajectory of moving from item-based to more schematic constructions. By contrast, the participant's use of gehen was characterized by schematic constructions almost from the beginning, suggesting a shortcut facilitated by explicit knowledge and processes. Both potential benefits and pitfalls associated with this alternative learning path are highlighted. The findings are explicated with reference to usage-based and complexity/dynamic-systems-theoretic concepts, thus offering an integration of explicit knowledge and processes in L2 learning and use into this particular theoretical framework.