Small-time and Second-string

Small-time adjective - Of minor importance.

Second-string and small-time are semantically related in minor topic. In some cases you can use "Second-string" instead an adjective phrase "Small-time".

Second-string adjective - Being a replacement or substitute for a regular member of a team.

Small-time and second-string are semantically related in insignificant topic. Sometimes you can use "Small-time" instead an adjective phrase "Second-string", if it concerns topics such as inferior, minor.