Wrong sadly...posted before but...the relevant UEFA regulations...
18.17 For all matches from the start of the round of 32, a club may register a
maximum of three new eligible players for the remaining matches in the
current competition. Such registration must be completed by 1 February
2010 at the latest. This deadline cannot be extended.
18.18 One player from the above quota of three who has played UEFA club
competition matches for another competing club in the current season may
exceptionally be registered provided that the player has not been fielded:
in the same competition for another club,
for another club that is currently in the same competition.
Furthermore, if the player’s new club is playing in the UEFA Europa League,
his former club must not have played in the UEFA Europa League at any
point in the current season.
He has played in Europe for another club currently in the same competition. And all player registration had to have been completed by 1st Feb so there's no opportunity to add him to our list anyway.
If Atletico had finished anywhere other than third in their Champs League group we'd have been OK.