In time and Second-string

In time adverb - Within an indefinite time or at an unspecified future time.

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

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

In time and second-string are semantically related. Sometimes you can use "In time" instead an adjective phrase "Second-string".