Why the best relegated players make the worst signings

James Ward-Prowse, Harvey Barnes and Jack Harrison will soon be on the move. Their suitors should be careful.

Every summer, the Premier League strips its fallen clubs of their most valuable assets. And every season, many of those star signings fail to capture previous form. What’s going on?

The answer might lie in, of all places, basketball - Alex Stewart explains.

The Premier League season has finished at last and talk has turned to the summer window. Clubs will be throwing money around: the heaviest-spending league in the world has seen another influx of capital (especially with Manchester United likely to be purchased), and GBE rules have been altered, allowing clubs to tap into foreign markets with greater abandon.

As a Southampton fan, I must confront not only the pain of relegation (although the promise of pleasure in the Championship glitters in the mist), but the impending loss of our best players. Roméo Lavia caught the eye, of course, but club captain James Ward-Prowse will likely attract the most interest this summer.

It’s easy to see why. Ward-Prowse was Southampton’s leading goal and assist provider last season, and the season before that, and almost the season before that (one behind Danny Ings), while his dead ball threat is unparalleled in English football.

This threat makes him undeniably an effective scorer and creator but, when the ball is in play, James Ward-Prowse is merely good, rather than great. His passing is fine, his defensive application good; his profile is solid at best. But because elements of his output – namely his whipped screamers from thirty yards - are so overwhelmingly eye-catching, Ward-Prowse is the kind of player likely to be overvalued, and return to the Premier League for much too large a fee.

Every summer, surviving Premier League clubs pick over the carcasses of relegated teams like vultures. And every summer, the most attention is paid to relegated players with the most output, like Ward-Prowse. The logic is clear: a player who scores or assists a lot in a team poor enough to be relegated should be better with better teammates. Better service means more goals; better strikers mean more assists. If only it were that simple.

James Ward-Prowse may grab the headlines, but Premier League history is littered with examples of the ‘best’ relegated players jumping back into the league and failing to perform, while less obvious purchases comfortably make the step up. The reason? Some players are ‘portable’, and others less so. And those with the most explosive outputs are often the latter.

To untangle this conundrum, we must delve deep into analytical theory and explain what ‘portability’ means, where it comes from and how Premier League clubs should apply it to accurately value their targets. And it all starts in another sport entirely: basketball.