Pjanic hit out at Koeman for a lack of respect after sealing a season-long loan move to Besiktas last week.
The 31-year-old Bosnia and Herzegovina international joined Barcelona from Juventus in the summer of 2020 but featured mainly as a substitute under the Dutchman.
Pjanic made 30 appearances across all competitions for Barcelona last season but failed to record a single goal or assist.
Koeman insists Pjanic is talking merely out of frustration as there were other players better than the former AS Roma and Olympique Lyon midfielder during his time at the club.
'I think it's a bit of frustration on the part of the player that I understand,' Koeman told Mundo Deportivo.
'But in our way of playing, in our ideas with the ball and without the ball, he has lost the battle with other midfielders, and nothing else.
'I wish him the best. It has been complicated. We have tried, we have tried and we have seen that there are other players better than him.'
Barcelona have begun the season with two wins and a draw in their opening three games.
