first-string

from WordNet (r) 3.0 (2006)

first-string
    adj 1: of members of a team; not substitutes
    2: being a regular member of a team; "first-string players"

from The Collaborative International Dictionary of English v.0.48

first-string \first-string\ adj.
   First to play in a game; not reserved as a substitute; -- of
   members of a team. Also used in non-sports contexts to mean
   {first-rate}.
   [WordNet 1.5 +PJC]