Second-string and Stand-in

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

Stand-in and second-string are semantically related In some cases you can use "Stand-in" instead an adjective phrase "Second-string".

Stand-in noun - A person or thing that takes the place of another.

Second-string and stand-in are semantically related in substitute topic. Sometimes you can use "Second-string" instead an adjective phrase "Stand-in".