second-string

Short definition from Wiktionary

Adjective

1. 1
   belonging to the second string of a team
2. 2
   substitute or replacement
3. 3
   second most important
4. 4
   Not as good; of a lower quality or condition.

Noun

1. 1
   A unit of players which is considered to have a secondary level of talent and which usually plays after the first string.