CLEVELAND — Major League Baseball is investigating the possible use of a forbidden electronic device by the Arizona Diamondbacks during their 11-8 win over the Colorado Rockies in the National League wild card game Wednesday night.

Ariel Prieto, a coach and translator for the Diamondbacks, was seen wearing an Apple Watch in the dugout during the game, which is prohibited by league rules. M.L.B. is trying to determine whether Prieto was using the watch to gain an advantage for the Diamondbacks or he had simply forgotten to take it off before the game started.

“We are looking into the situation,” an M.L.B. spokesman said Thursday.

The Diamondbacks said in a statement that Prieto had inadvertently, and innocently, worn the device on the bench.

“Ariel Prieto has assured us that this was a simple oversight and honest mistake,” the statement said. “The watch he wore last night was absolutely not used in any way related to our game, and we will make certain prior to the NLDS that it will not be an issue again. Ariel takes full responsibility and feels terrible that this has been a distraction of any kind.”