Bielsa begrudgingly granted the right-back's wish despite his side's injury crisis as he did not want to keep a player against his will.
However, the Leeds boss said: "I did not think he needed to play games elsewhere. He was a player who was very necessary with all of the absences we have.
"In a situation when opportunities for youngsters have increased, Drameh would prefer to experiment outside our team.
"Clearly, I calculated things wrongly because what I consider as a great opportunity, those who are benefiting from that position, they prefer to abandon the club looking for another type of competition.
"Evidently, what I imagined as a great chance, they don't.
"Perhaps I overvalue that you're in a 20-man squad in the best league in the world.
"Of course with a player leaving it's one alternative less. But when a player wants to leave, there's no point trying to keep them"