The duo worked together in the Premier League at Chelsea, and the Portuguese coach was forced to sell the Netherlands international winger due to his constant injury problems
The Dutchman spent three years at Chelsea under the Portuguese's tutelage, helping the Blues win two successive Premier League titles.
However, according to Mourinho's spokesman, the 49-year-old has always felt that the Bayern Munich winger lacked the correct mentality, and grew tired of the Dutchman's constant injury problems.
"Jose has always said it: Arjen simply lacks character, and the absolute will to win," Eladio Parames told TZ. "After the smallest knock he could not play, and Jose had to let him go."
Bayern Munich and Real Madrid will compete for a place in the Champions League final on Wednesday, with the German outfit holding a 2-1 lead from the first leg.