According to French reports, United will turn their attentions to PSG striker Edinson Cavani due to the faintness concerns of Falcao.
The Colombian goal scorer has been sidelined through a calf injury since Oxtober, missing vital games against Manchester City, Arsenal and Chelsea.
However previous to his injury, he still managed just one goal from five Premier League games.
The Red Devils’ decision not to spend £43.5m to keep Falcao at Old Trafford has put PSG on alert, as the Ligue 1 champions are thought to be willing to offload Cavani and bring in Falcao.
United have been linked with Cavani for some time after the Uruguayan has reportedly been having fall-outs with boss Laurent Blanc over where he is being played.
Meanwhile Louis Van Gaal is thought to be readying a £50m swoop for the PSG star.
By Phil Wellbrook