Lesser and Second-string

Lesser adjective - Having not so great importance or rank as another.

Second-string and lesser are semantically related in inferior topic. In some cases you can use "Second-string" instead an adjective "Lesser".

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

Lesser and second-string are semantically related in importance topic. You can use "Lesser" instead an adjective phrase "Second-string", if it concerns topics such as insignificant, subordinate, minor, under.