With the news that Falcao is set to miss another big game for Manchester United, at what point does the loan deal begin to look bad for United and Louis van Gaal?
The Old Trafford club invested almost £19m to rent the Colombian international for the season - a £6m up front fee and £265,000-a-week wages. They also retain the right to buy him for a further £43m.
That was an incredible bet on a player with a chequered injury history returning from major ACL damage suffered in January 2014. Real Madrid passed, Barcelona went for Luis Suarez, Chelsea for Diego Costa.
Van Gaal took the gamble and so far it's yet to pay off. Falcao has played just 251 minutes of Premier League football this season, contributing one goal.
Although it's through no fault of his own, Falcao was fit for the lesser important games of United's early season schedule - Everton and West Ham at home, Leicester away.
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He's missed all the big games though - Manchester City away, Chelsea at home and now Arsenal at the Emirates Stadium - the matches van Gaal signed him to directly influence.
Falcao can't control that, but it illustrates the huge risk United took when they splashed out on the unorthodox loan deal. In theory, it insulates them against further risk - after all, it would have been a nightmare for United to sign Falcao for £43m and then lose him for the season.
But they've still invested £19m.
Monaco injury management
Having missed eight months through injury and recovery, Falcao's return to action for Monaco was carefully managed through to the Emirates Cup friendly tournament in August.
He returned and looked sharp, scoring on the Sunday. But then, all of a sudden, he was made available by Monaco. They either knew something others didn't or Falcao demanded a move.
That's possible, after all he watched on as James Rodriguez left the club, but it's unlikely Falcao's ambition upon signing for Monaco was anything other than financial. He had the super-wage and the tax situation others could only dream of even when the opportunities to join the likes of Madrid, Chelsea and United presented themselves.
On deadline day, Manchester United took the plunge others - notably Real Madrid - were not willing to make.
Now they're left with the bill while Falcao has to ice his knee after every training session. That does not sound like an injury that has fully healed, or a situation that you'd want to pay £19m to buy into.
United players have reportedly been left stunned at the amount of treatment Falcao needs to get him into playing shape, but for a player who has had three serious knee injuries, those in power at United surely knew the risks.
Current injury status
Currently it's a calf problem that is keeping the Colombian on the sidelines. That will be frustrating for the club, the player and the fans but it's not the real problem.
United signed Falcao to be the difference maker, along with Angel Di Maria, that would prevent a repeat of last season's seventh placed Premier League finish.
The English giants currently sit in exactly the same place, without their marquee deadline day signing for the campaign's biggest games. We're only 11 games in, but United have Falcao on the payroll for just one season and they've paid £19m for the privilege.
It's no time to worry just yet, but if United can't get Falcao fit for the big games, it's going to begin to look like £19m wasted.