Chelsea's over-reliance on Reece James is a serious problem for Graham Potter

What should have been a relatively stress-free evening for Chelsea fans became exactly the opposite when right-back Reece James was substituted off in the 53rd minute against Bournemouth on Tuesday night.

An otherwise comfortable 2-0 win - ending Chelsea's run of three straight defeats - was marred by another knee injury to James in his first game back after missing the World Cup with England, where he would have been nailed on to start somewhere in Gareth Southgate's defence - full-back, wing-back, or centre-back.

That neatly summarises where we are with James. He's so good he has to be in the team, whichever position he plays. And he can perform, even excel, in a fair few, as a marauding one-man force down the flank, a box-to-box midfielder or even a ball-playing defender.

Most players suffer as a result of their versatility. Not James. His skill set is such that Chelsea have perhaps inadvertently built their entire attacking structure around his forward runs from right-back, along with his ball-carrying, passing range, shooting and ability to cross accurately from deep or right up towards the goal line.

In short, this latest injury is not good news. It is no exaggeration to say that if it's serious, and there is no way of knowing yet outside of Chelsea's physio room, it has the potential to derail the rest of Graham Potter's season at Stamford Bridge.

After James limped off just after the hour mark against AC Milan on October 11, again during a run-of-the-mill 2-0 win, Potter's bright start at the Bridge immediately began to crumble around him.

A fortuitous win over Aston Villa followed, with Raheem Sterling starting at right wing-back before a switch with Ruben Loftus-Cheek, two round pegs shoved into a square hole.

Without James handling the entire right side, Chelsea were a mess both offensively and defensively and a string of poor results (unsurprisingly) followed. Only the relative minnows Red Bull Salzburg and Dinamo Zagreb were narrowly beaten in the Champions League - simply not good enough given Chelsea's ambitions and the money spent during the summer window.

Most damning was the 4-1 hammering by Potter's former employers Brighton & Hove Albion on October 29.

The first and third goals came down Brighton's left flank, where they had joy all afternoon, in wide-open spaces Trevoh Chalobah couldn't defend on his own. Christian Pulisic, ostensibly the starting wing-back, may as well have not been playing.

Arsenal had a field day down that side against Loftus-Cheek, Azpilicueta and Chalobah despite a 1-0 scoreline. It was a similar story against Manchester City in the Carabao Cup, when Julian Alvarez sealed a 2-0 win by drifting in off the left, completely unmarked by either Kalidou Koulibaly or Loftus-Cheek.

Again, Chris Willock's winner for Newcastle a few days later saw him start high on the left and simply wait for Chalobah to get distracted, granting him enough time and space to pounce upon a loose ball on the edge of the area and smash home.

Would James alone have prevented these goals? Maybe not, but it's worth noting that his absence caused a typically imposing back five to start playing like a pub team. Particularly Marc Cucurella, who looked suddenly and spectacularly unsuited for a role he was performing perfectly well in for Brighton last season.

That's just on the defensive side of the ball. Going forward, minus James, Chelsea have been almost exclusively toothless, with goals in the Premier League since his injury coming from a gift-wrapped Tyrone Mings error, a free-kick, a penalty and a Conor Gallagher cross from exactly the sort of positions James would usually occupy.

Chelsea looked a completely different team against Bournemouth following the World Cup break. Potter lined up his team in a 4-2-3-1 shape, a move away from his favoured 3-4-3 or 3-5-2, with a rare start for Denis Zakaria as part of a two-man pivot alongside Jorginho.

The system brought the very best out of Mason Mount, given the freedom to drop deep or run in behind as a 10, and Kai Havertz, who is often criticised for not being a natural centre forward yet led the line with aplomb.

James, as always, was a menace from full-back, linking up well with Sterling down Chelsea's right. The whole starting line-up appeared freed by the system change, which Potter may now have to immediately scrap if James is out for any serious length of time.

Azpilicueta, at 33, just can't cut it as a Premier League full-back in a back four at this point, certainly not against either Phil Foden or Jack Grealish come Man City on January 5. Fulham, Crystal Palace and Liverpool all present their own unique conundrums after that.

The problem is that James appears to be the lynchpin holding everything together for Chelsea at the moment. He's the heartbeat of this team. Without him, Potter will likely revert to a system for which his players seem ill-suited while adding both Azpilicueta and Chalobah to what was a solid back-four against Bournemouth could create more problems than it solves.

It is systematic of poor long-term strategy, squad planning and the scattergun recruitment at Stamford Bridge that Chelsea are even in this position, completely reliant on a 23-year-old injury-prone academy product, despite spending close to £300 million in the summer window alone.

No team with that amount of resource should have to resort to playing Loftus-Cheek, Sterling or Pulisic at right wing-back, to put it mildly. It's not an oversight either, a sudden realisation after Potter jumped ship from Brighton. Thomas Tuchel played almost exclusively with wing-backs too. Azpilicueta's form has been a concern for a while. There are no excuses.

Chelsea now find themselves crossing their fingers and hoping for the best. It leaves them in a delicate situation.

Cover is urgently required in January, sooner rather than later. Chelsea can't go into the New Year with Azpilicueta as starting right-back, let alone the only fit right-back in the squad. They must now be able to find someone good enough for a Champions League-level team yet happy to accept a backup role once James returns.

Those sort of players don't grow on trees. Could Croatia's World Cup star Josip Juranovic be tempted? How about Solly March, who Potter knows inside and out? They're hardly players that get the pulse racing but that may well be the calibre Chelsea are restricted to as a stopgap, short-term solution.

Is there a long-term solution out there anywhere near as good as James? Able to lock up a player like Rafael Leao in the Champions League?

Narrator: there isn't.

For now, all Chelsea can do is hope this is just another temporary setback for their best player and the man upon which the rest of their season depends. If it isn't, things will start getting ugly again and Potter may soon find the patience start to run thin.