Teams notified players Friday this may the final year of the designated hitter, prompting an angry response from the players’ association.

Management negotiator Randy Levine emphasized owners have not made a final decision on the DH, which has been used by the American League since 1973. Levine said owners opted to send the notification Friday only because baseball’s current labor agreement requires one year’s advance notice for a unilateral change to the playing rules.

“What is crystal clear, your comments notwithstanding, is the warning shot you have just fired,” union head Donald Fehr wrote in a letter to Levine, a copy of which was obtained by The Associated Press. “I must and will advise the players you have chosen to set the stage for and begin these discussions with a threat.”

The fate of the DH is tied to the future of interleague play. Under the current labor agreement, interleague play ends after this season, but owners want to extend it.