In the multibillion-pound industry that is the top end of professional football, for better or worse it's transfer activity that attracts the most attention among investors, owners, managers, sporting staff, media and supporters alike. And although the transfer window doesn't reopen for another couple of months, planning is already well under way as clubs strive for a positive response to intense scrutiny.

Assessing the past year's performances is the prime focus as the season draws to a close. Whether a team has been competing for honours, fighting to beat relegation or sitting safely — or disappointingly — in mid-table, clubs are busy identifying the ins and outs that could make next season more successful.

With the "untouchables" usually well-known, the discussion revolves around who to keep and who to let go. The latter are either softly launched as unofficially available (i.e. "listening to offers under the right circumstances"), which is where agents play a vital role, or actively encouraged to search for new opportunities.

As the very nature of sport means that while a few succeed, others fail, it's logical that some teams hit gold with their recruitment whereas others will count the cost for years to come. For a variety of reasons, some signings just don't work out and those involved are better off parting ways once the transfer window opens.

Here's a look at some of these at the top end of the Premier League; all big-name internationals with impressive CVs, sizeable wages and huge transfer outlay, meaning the clubs — and the players' agents — need significant and coordinated work (along with some goodwill on either side) to make the moves happen.

Christian Pulisic, 24, attacking midfielder, Chelsea

Despite all the managerial comings and goings, the United States international seems no closer to a regular first-team slot at Chelsea. Having arrived at the age of 20 under Maurizio Sarri's leadership, Pulisic has failed to build on his promising debut season — in which he produced nine Premier League goals — and it's fair to say that he has been in a slow decline ever since.

The youthful freshness that made him so effective in offensive one-on-one situations has wavered, just as his dynamic and effortless interactions with the left-backs and midfield runners have suffered with the unsettled nature of the Chelsea squad. Increased competition for his favoured left-wing role has not helped his cause either.