Dmitry Poloz, 26, was selected for the test at Celtic Park at full-time but failed to turn up straightaway, earning his side a caution from European football’s governing body.
Uefa regulations require players selected for drugs tests to go straight to a specially assigned doping control room after the game, but Poloz instead entered his team’s dressing room, “through habit”, according to his club.
“Uefa did issue a warning to the club - that is standard procedure when the doping officer includes it in his report.
“In this case our player, Dmitry Poloz did not have time to stop and he went to the dressing room through habit,” Zenit said in a statement.
However, Zenit claim the player was sent to the test immediately by medical staff, and it is believed the warning from Uefa is only to ensure the mistake doesn’t happen again.
Poloz played no part in the game itself or the return leg, where his side mounted an impressive comeback to win 3-0 and proceed to the last 16 of the Europa League.
Zenit have since exited the Europa League at the hands of German side RB Leipzig.