Second fiddle and Second-rater

Second fiddle noun - A secondary role or function.

Second-rater and second fiddle are semantically related In some cases you can use "Second-rater" instead a noun phrase "Second fiddle".

Second-rater noun - A person of second-rate ability or value.

Second fiddle and second-rater are semantically related in sidekick topic. You can use "Second fiddle" instead a noun phrase "Second-rater".