Forlan had a difficult time while he was with United.
"He played in England of course when he was younger and he has quality so it's a matter of time and he will be playing really well," he told AFP.
"It's difficult to adjust - new manager, some new players.
"They have some good players and of course you need time for everybody, but unluckily in football, time is not what you have every time.
"But I think the directors and everybody knows that this could happen and that some games you have to be patient."