Felix is available on loan for the remainder of the season. He has fallen out of favour under Diego Simeone at Atletico Madrid.
Arsenal are keen on signing both a striker and a wide player. Atletico would demand a large loan fee to facilitate a deal.
Ndicka is out of contract at Eintracht Frankfurt at the end of the season. Arsenal are linked with a potential pre-contract agreement, signing him on a free transfer in the summer.
However, while the window is open, the chance of a deal happening this month cannot be ruled out. Frankfurt may be keen to recruit some money for the Frenchman to prevent losing him for nothing.