Manchester United had been linked to multiple right-backs - including Josip Juranovic - in the build-up to the January transfer window, but after Aaron Wan-Bissaka's good form they moved on to other targets.
Transfer guru Frabizio Romano said: "We know they were looking for a new right-back, and that Aaron Wan-Bissaka could have left because he had a difficult first half of the season. But then what happened was that he played well in January and Manchester United decided to stick with him and invest in Wout Weghorst and Marcel Sabitzer instead.
"Still, United had a right-back in mind in case Wan-Bissaka was going to leave, and that right-back was Josip Juranovic was their preference, top of the list to come in as backup right-back, behind Diogo Dalot, who remains the owner of the right flank at the club.
"The United board discussed Juranovic, but they decided to keep Wan-Bissaka and so the deal collapsed and he instead decided to accept the approach from Union Berlin. Still, he was a concrete opportunity."
