In the multi-billion-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.

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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's been in a slow decline ever since.

The youthful freshness that made him so effective in offensive one-vs.-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.

While the American may end up looking back on the past two years as lost campaigns, with one-year left on his Chelsea contact at 24 years old, there's every chance of resurrecting his faltering career. But that mission is more likely to take place elsewhere.

Harry Maguire, 30, centre-back, Manchester United

Signed by Manchester United for £80 million from Leicester City in 2019 -- still the world record fee for a defender -- there's little to suggest that Maguire is facing anything other than an uncertain future. With a meagre seven Premier League starts this season, the England centre-back (and club captain) finds himself clearly behind Raphael Varane and Lisandro Martinez in the pecking order, while Victor Lindelof's impressive outing in the FA Cup semifinal might even make the Swede more likely to win manager Erik ten Hag's trust going forward.

While a lot has been made of Maguire's improved statistical output this season -- which can also be explained through him mainly starting against lower half sides, let alone a smaller sample size -- the irrefutable fact of Maguire's shortcomings in handling the ball, lack of pace and agility on the turn remain irreconcilable with ten Hag's idea of defending (high line, play out expertly from the back.) And as much as the Dutch head coach deserves credit for the minor progress in the centre-back's game, there are limits to how much a 30-year-old can improve his touch, under-pressure passing and general physical ability.

Donny van de Beek, 26, central midfielder, Manchester United

The Netherlands international arrived at Old Trafford in the summer of 2021 for £35m with significant expectations, following two outstanding seasons for Ajax. Admittedly, injuries have played a part in the box-to-box midfielder's lack of progress in a Manchester United shirt, but few would have foreseen him not even reaching 10 Premier League starts three years later.

Even the most positive-minded followers of United would struggle to find mitigating reasons to extend the Dutchman's stay at Old Trafford; not only does he look unable to make more than a sporadic impact on the games, but also his well-documented positional sense in and around the box from his Ajax days -- and finishing with confidence -- has dwindled to the point of extinction.

If there were any remaining doubts as to whether a second or third chance were due, even the arrival of his prior head coach ten Hag didn't improve matters -- neither did a largely forgettable loan move to Everton.

Philippe Coutinho, 30, attacking midfielder, Aston Villa

Since leaving Liverpool five years ago, Coutinho's career trajectory has followed a curious pattern -- early promise followed by fading contribution followed by promising loan spells, which in turn have ebbed out into not much. While it's hard to blame Aston Villa for making the Brazilian's loan move permanent -- given the life he injected into a lethargic Villa side and doing his bit to secure enough points to stay clear of relegation -- the ensuing step of handing a four-year deal to a 30-year-old with a dubious career trend, is less understandable.

Coutinho has failed to find a suitable role in Unai Emery's side and even the die-hard optimist would admit it's hard to make a case for the creative attacking midfielder to become more than a squad player for the demanding head coach. He scored his only Premier League goal of this season in the 4-2 home defeat at the hands of Arsenal -- his last game before picking up a hamstring injury which is still keeping him out.

Kalvin Phillips, 27, defensive midfielder, Manchester City

With just 109 minutes Premier League minutes played (without a single starting appearance) this season, there's no denying that the England midfielder's move from Leeds has hardly been a successful one. When given a rare start in cup competitions, Phillips has hardly impressed.

Moreover, whenever the 27-year-old is brought on during the second half, the structure of the midfield tends to disintegrate, with the quality and the intensity of the ball circulation dropping noticeably too. That's not necessarily down to Phillips not doing his job properly, but rather that the No. 1 choice for those tasks -- Rodri -- does them to world-class standards.

Regardless of business Manchester City do this summer, Phillips is still unlikely to end up any nearer to a regular starting spot for the club (the introduction of John Stones as an "ad hoc" central midfielder further complicates his situation.)

As much as it's not problematic for Man City to keep Phillips on as a highly paid, (homegrown) squad player, for a player in his prime with an England career to take care of, however, a move -- loan or permanent -- seems the logical outcome.