Why so?
According to section 18.07 of the UEFA CL regulations:
"As a rule, a player may not play in a UEFA club competition (i.e. UEFA Champions League and UEFA Europa League, but not UEFA Super Cup) for more than one club in the course of the same season. Exceptionally, however, a player who has been fielded in the first, second or third qualifying round of the UEFA Champions League or UEFA Europa League is entitled to play in the UEFA Champions League or UEFA Europa League for another club as from the group stage, provided that his former club did not qualify for the group phase of either the UEFA Champions League or the UEFA Europa League"