How do you judge whether a player is a flop?
Firstly, they have to be a key man in that side. Maybe the team's best player, maybe the most influential.
They have to be someone with a reputation, preferably built on past success, otherwise what to do judge them against?
What is their job and how effectively have they done it? To not be considered a flop they must consistently deliver the goods.
Strikers and goalkeepers are an obvious target for this sort of study as it is easy to measure their contribution to the side.
There are a number of candidates based on their displays this season compared to last.
Norwich City's Grant Holt has struggled to repeat his heroics of 2011/12 when he scored 15 Premier League goals (17 overall). This time round he has scored five times 26 in appearances in the league.
Other under-performing front men include Pavel Pogrebnyak.
The Russian blitzed his way onto the Premier League scene last January with Fulham by scoring five goals in his first three games.
Danny Graham has also failed to live up to the hype.
Then there's dear old Fernando Torres.
Although his tribulations in the Premier League still continue, his goal return is not that bad when you factor in his contribution to Chelsea's cause in other competitions.
Besides, everyone's sick of hearing about how he's not the same player he was.
My choice does have a link with Torres.
And it's Carroll who takes this award. And here's why.
A striker that does not score many goals is asking for trouble.
Carroll has three from 16 Premier League appearances for the Hammers (18 if you include his two for Liverpool at the start of the season) and only one of those has been in a winning cause - against Swansea.
Over the last 12 months he has scored four times in 27 matches (via soccerbase.com).
His first goal of this season came in West Ham's 3-1 defeat at Tottenham in November 2012—his first for 15 games (around 20 hours) all told.
To Carroll's credit it is not for the want of trying.
No-one in a West Ham shirt has had more shots than Carroll so far this season. He has 46, which averages out at just under three per match (via Whoscored.com).
When Carroll joined West Ham at the start of the season it looked like the Hammers had pulled off one of the biggest coups of recent times.
Here was a £35 million striker joining a newly-promoted club with debts as tall as the Upton Park floodlights.
The Hammers agreed a two million pounds loan fee for Carroll and covered his wages - reportedly around £85,000-per-week.
So over the course of the season that represented an outlay of approximately five million pounds.
As part of the deal West Ham have an agreement to make Carroll's move permanent in the summer for £17 million.
It is that part of the equation that has, understandably, got the Hammers's co-chairmen David Sullivan and David Gold checking the small print.
Before the start of this season, spending £5 million for a striker with Carroll's reputation was a viable punt even if the Hammers ended up getting relegated.
As it has turned out Carroll's underwhelming form in front of goal has worked out at around £2 million per strike.
It may be a bit unfair to criticise Carroll's fitness record as no-one can help getting injured.
However his struggle to stay healthy has hampered his all-round game and greatly reduced his threat and his chances of building any momentum.
The hamstring injury he picked up in his debut match against Fulham kept him out for a month meaning he was not able to build on an impressive first appearance.
A knee problem then sidelined him for another nine weeks at the turn of 2013.
Each time he has returned he has had to, in effect, start his season again.
It is not Carroll's fault but it is another important reason why his move has not been a success.
Once upon a time, Andy Carroll was the hottest property around.
Back in 2009/10 Carroll led Newcastle's romp into the Premier League with 19 goals.
The following season he silenced the doubters by proving he could cut it in the top flight by banging in 14 more at an average of nearly one-every-other-game (via soccerbase.com).
He scored a hat-trick on his home Premier League debut. He was a hero.
Everyone knew Liverpool had paid over the odds when they shelled out the enormous fee they did in January 2011 but the alarming plummet in his form that accompanied his move to Anfield has never really left.
His 11 goals in 58 games for the Reds says it all.
Carroll's job is not just to score though. He also must act as a target man. At West Ham that is almost as important as scoring because of the way they play.
However Carroll's ability to hold the ball up has not been great.
He has been dispossessed 32 times this season and given the ball away on 27 occasions (both via Whoscored.com).
His time at Upton Park has suggested his overall slump is not about to end soon.
This is Andy Carroll's fourth season since shooting to prominence for Newcastle in the Championship three years ago.
Yet do we really know much about him? How good is he? Is he just a flash in the pan? Was he ever really worth it?
What's sad is that we may never know, because where is his career now heading?
Assuming West Ham do not make his loan move permanent, where does he go?
He has no future at Liverpool and a return to his spiritual home at St.James' Park looks unlikely given what's happened to him since he left.
At West Ham it was all set up for him to rebuilt his career.
He joined a club with a manager who rated him and one captained by his best mate.
More importantly he was playing for a team that was prepared to build its strategy around him. He was the main man.
Upton Park seemed like the perfect fit for Carroll and, for an hour of his debut against Fulham, it looked like the ideal marriage.
Over the course of the season, though, he has just not been able to make it work long term.
He could yet change that by finding his form over the closing weeks of the season but he does not appear to have won the trust of the Hammers board.
They will now only consider a deal for him if it's worth substantially less than the £17 million initially agreed with Liverpool.
In monetary terms, and footballing ones, it is quite a fall from grace.