OFFDAY

Set to 3 different clues across 3 published puzzles, most often “When one's not at one's best” — The New York Times, Thursday, 4 December 2003.

6 letters

Every clue on record, most used first

When one's not at one's bestonce
The New York Times — Thursday, 4 December 2003
When things don't go rightonce
The New York Times — Thursday, 22 February 2001
0-for-5 performance for Mark McGwire, e.g.once
The New York Times — Sunday, 24 September 2000