second string

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The group of players that substitute for the starting players or from which substitute players are drawn on a sports team.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun sports A unit of players which is considered to have a secondary level of talent and which usually plays after the first string.
• adjective idiomatic Not as good; of a lower quality or condition.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a squad of players that are available either individually or as a team to relieve or replace the players who started the game