This study examined the influence of higher education teacher training on student physics teachers' progression in content knowledge (CK). To become experts, student teachers must acquire both declarative and procedural -- conditional CK. This progression is generally characterized by the prerequisite role of declarative knowledge, meaning that declarative knowledge influences procedural -- conditional knowledge exclusively. The progression in declarative as well as procedural -- conditional CK requires special support, due to the complexity of physics. This special cognitive support is assumed to enhance student teachers' CK development by reducing complexity and cognitive demand. To date, however, it has been unclear how cognitive support contributes to student physics teachers' declarative and procedural -- conditional CK development. To address this issue, we analyzed data across one year of higher education teacher training of student physics teachers (N = 107). We used a cross-lagged model to examine the development of declarative and procedural -- conditional knowledge under the influence of cognitive support. Our findings revealed that the development of student teachers' declarative and procedural -- conditional CK is intertwined. Interestingly, cognitive support only influenced the development of procedural -- conditional CK. This implies that higher education teacher training should provide cognitive support to promote student teachers' progression toward CK expertize.