The 29-year-old signed for United in a big-money season-long loan deal from Monaco on transfer deadline day in September, but has struggled to make an impact at Old Trafford, and was selected to turn out for the Under-21 team against Tottenham last week.
Silvano Espindola has told AS Colombia that Falcao, who has scored only four goals in 21 appearances for United, did not understand the decision, and is deeply upset by the position he has found himself in.
United manager Van Gaal has insisted the decision to select him was not a humiliating one for Falcao, but Espindola remains unconvinced.
"He is a coach that kills your confidence," Espindola said
"He destroys it
He is working with other great players that were at a great level and with Van Gaal they are now less so."
Espindola said his former client was clearly upset when he and the frontman spoke ahead the match, in which Falcao struggled and was replaced after 71 minutes.
"I am not going to say that he feels happy because he isn't
We talk a lot and we cry together," Espindola said
"It's not an easy situation because every player wants to play and every goalscorer wants to score goals."
United paid a reported Â£6million loan fee for Falcao, as well as covering his hefty wage, and must decide whether to take up a Â£43.5million option to make the deal permanent in the summer
Falcao missed much of last season and the World Cup with a knee ligament injury - the second of his career - but Espindola does not believe that is a factor in his Old Trafford struggles
"The injury is forgotten," he said
"The main problem is the intensity of the game
He has to get this intensity back
The problem isn't fear of another injury, it's a lack of rhythm."
Source : PA