Goalkeepers. That is my one-word answer to those people who believe that it is impossible for free markets to value something incorrectly for any length of time.

Many of the transfer and wage figures that make it into the public domain make sense to me. Sometimes individuals seem a bit pricey or too cheap, but that may be because we haven't seen the full deal or we don't understand the cost of the risk being taken.

So English players may seem overpriced, but they come with a smaller risk that they won't adapt to English football.

But this isn't true of goalkeepers. Keepers come cheap. And our figures suggest that they shouldn't do. Over years of working on player value, the Fink Tank has reached the conclusion both that a very good goalkeeper makes a huge difference and that a poor one is a massive disadvantage. Of all the players, buying a good 'keeper is among the most important. Yet the price is low. Go figure.

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• GRAPHIC: Fink Tank

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These thoughts were prompted by this year's Fink Tank Player of the Year. As we do at the end of each season, Dr Henry Stott, Dr Ian Graham and Dr Mark Latham have taken every on-field action and tracked the relationship between these actions and the points that each team obtain. Then they have simulated the Barclays Premier League campaign again and again, each time removing a player and seeing the difference to the outcome without them.

The final result is a table of the number of points added by each player compared with an average player in the same position playing for an average team. A significant component of the rankings we do is the time spent by each player on the pitch. We could eliminate this element and you would do if you wanted to see who was the most valuable player at any given time. But we want to see who did best this season, so ability to stay injury-free and be picked is important.

The ranking is on the graphic. The clear winner is Petr Cech, the Chelsea goalkeeper, someone who hasn't been mentioned by other pundits but who has finished near the top of the Fink Tank table year after year. Just behind him is Frank Lampard. The England midfield player finishes near the top every season and over a five-year period has certainly been the Premier League's best player.

Let's have a look at the different areas of the field. Just behind Cech in the goalkeepers' rankings is Mark Schwarzer. Next comes Heurelho Gomes, in whom Tottenham Hotspur fans had so little faith not too long ago. Tim Howard is fourth, edging out Edwin van der Sar partly because he has played more.

Nemanja Vidic heads up the defenders' ranking, with John Terry second (relatively poor for him). Bacary Sagna is third, followed by Rio Ferdinand and Jamie Carragher.

Lampard tops the midfield players, narrowly beating Steven Gerrard. Cristiano Ronaldo is next, followed by Xabi Alonso. Denilson, perhaps controversially, comes fifth.

Then there are the forwards. Nicolas Anelka is the winner and Robinho is runner-up. If Robinho had played more, he would have been top, an answer to those who think he has been a disappointment. Next comes Wayne Rooney, then Dimitar Berbatov. Finally, even in his relatively poor season, Emmanuel Adebayor comes in fifth among forwards.

A couple of other interesting points. Carlos Tévez was one of Manchester United's weakest players. And Deco did pretty well when he was playing.

Finally, the great (consistently so) Martin Laursen was Aston Villa's best player. He'll be missed.