Radamel Falcao had no shots at goal in Manchester United's 3-1 win over Preston

It was the Preston fans who chanted "what a waste of money" at Radamel Falcao on Monday night.

But you could not really blame Manchester United manager Louis van Gaal if he thought the same after the expensive striker's latest ineffective display.

Time is running out for the £6m loan signing from Monaco, who has until the end of the season to persuade Van Gaal to fork out £43.5m to make his deal a permanent one.

Right now, the chances of that happening look minimal, at best.

Far from justifying his £265,000-a-week wages, Falcao has scored just four goals in 19 games for United, and has completed 90 minutes a mere four times in five and a half months at Old Trafford.

Are United better off without him? They were against League One side North End, who led until Van Gaal hauled off the Colombian after an hour and saw his reshaped team fight back to win 3-1 and reach the FA Cup quarter-finals.

And with only 13 Premier League games and the rest of United's FA Cup campaign left of the season, maybe the real question now is how many more chances will Falcao get?

"Another night of nothing from Falcao," pondered BBC co-commentator Martin Keown as the 29-year-disappeared from the Deepdale pitch.

"You wonder if you will see him again in a Manchester United shirt. I don't think he has offered much at all."

Tamed by a League One defence

Falcao certainly did not offer any shots against Preston, either on or off target. It was the same story in United's last Premier League game against Burnley as well.

The worry for United, but maybe especially for the player himself, is just how easily he was marshalled by a League One defence.

For a player who has starred for Colombia and been a leading light in Portugal, La Liga and Ligue 1, his movement was poor, and too easily tracked by Preston's three central defenders.

When partnered with Robin van Persie, as he has been recently, that lack of raw speed has left United looking blunt up front, and he fared little better on Tuesday night when leading the line on his own.

Falcao at Manchester United Appearances: 19 Minutes played: 1,148 Goals: 4 Minutes per goal: 287 Assists: 4 Bookings: 2

Lack of service at Deepdale was a factor in his failure to shine again.

He was rarely involved and had only 26 touches, but he looked slow on the ball when he came looking for it outside the box and did not react quickly enough when he was inside it either.

"He just did not have the pace to get away from the Preston defence," said Keown.

"Is he fit enough? He's trying to prove he should be here in the long term but it's just not coming off for him."

United have an option to activate a £40m buy-out clause for Falcao (left) who earns £265,000 a week

Still chasing full fitness

Falcao missed last summer's World Cup because of a serious knee injury and the more you see of him, the more you wonder how much of a toll that is still taking.

He has been hampered by a calf injury in recent months but even when injury free, that long lay-off means he is still chasing full fitness.

More than any other position, strikers need sharpness but Falcao seems short of that, and has done since his arrival.

Van Gaal questioned his fitness in December when he declared his deadline day signing was only able to play for 20 minutes at a time.

At the time he was using him only as a substitute, and the situation did not seem to improve when he left him out of his squad completely for United's 1-0 home defeat by Southampton on 11 January, then said he preferred 19-year-old James Wilson up front against Stoke the following week.

Falcao has found the net since then, in a 3-1 home win over Leicester, but his overall contribution will have done little to convince Van Gaal that he is a part of his team's long-term future.

Van Gaal's other options

If Wilson has the pace that Falcao currently lacks, United's other striking options have other attributes the Colombian is also without.

Van Persie has greater guile in the area; Wayne Rooney is a better passer and harder worker outside it.

Both look more of a goal threat than Falcao, which makes it even more inexplicable that Van Gaal seemingly prefers the latter to operate in midfield.

Marouane Fellaini is only an emergency alternative but, as he showed against Preston, he has the aerial power to make a difference when needed.

Where Falcao fits into all of this is unclear.

An uncertain future

The suggestion from Falcao's agent Jorge Mendes at the start of the year that his client may not be at Old Trafford at the start of next season is looking even more likely with each passing week.

Mendes's assertion that Falcao "will play in one of the very best clubs in the world next season whether that is United or not" does not look quite so nailed on.

For more than £40m, let alone his weekly salary, you would presume there will be few takers based on what we have seen so far on these shores.