The loss of the 21-year-old, who did not travel with the rest of the squad to the Club World Cup in Japan, is a huge blow for the Blues.

He and John Obi Mikel are the only genuine holding midfielders in Rafael Benitez’s squad, something that always threatened to become an issue after Raul Meireles was sold and Michael Essien and Josh McEachran were allowed to leave on loan.

To make matters worse, Mikel is in the midst of a three-match domestic suspension on top of what might be a month-long absence for the Nigeria midfielder when he begins African Nations Cup duty in January.

Benitez could ask Mikel’s national team bosses not to exercise their right to call him up two weeks before the tournament begins but such pleas have fallen on deaf ears in the past for Chelsea when it has come to other African players.

All that means interim manager Benitez could now make signing reinforcements his top priority in the January transfer window.

Chelsea have previously been linked with Everton star Marouane Fellaini, who would command a hefty fee following a stunning start to the season.

Alternatively, they could attempt to cut short Essien’s season-long loan at Real Madrid or McEachran’s similar spell at Middlesbrough.

However, part of the reason Essien was allowed to move to Real is because of his own recent injury record.

He was even forced to return to Chelsea to train this month after seemingly suffering a bad reaction to some medication while in the Spanish capital.

McEachran has impressed at the Riverside but he arguably does not possess the same ball-winning qualities as Romeu, Mikel and Essien.

One player who does – and who might be asked to fill the void for a time – is David Luiz.

Benitez last week did what three of his predecessors were not bold enough to attempt and experimented with Luiz in just that position.

The Spaniard also confirmed after Wednesday’s Champions League thrashing of Nordsjaelland that he would consider doing so again if the need arose.

But not even Benitez could have foreseen the seriousness of Romeu’s injury, which came as a real shock to Chelsea.

They had been hoping as recently as yesterday that the midfielder would recover in time to join them in Japan, despite him having limped off after just 20 minutes on Saturday.

Chelsea’s decision to allow several big-earning players to leave in recent years ultimately helped them turn a profit for the first time since Roman Abramovich bought the club put them on course to meet Financial Fair Play targets.

However, they have also ended up with one of the thinnest squads of any big club, something that has arguably already cost them.

Injuries and suspensions to John Terry, Frank Lampard and Daniel Sturridge have left them desperately short of options in key areas and certainly contributed to their worst winless run in the Barclays Premier League for 15 years.

Terry and Sturridge remain sidelined but Lampard made his long-awaited comeback from a calf problem on Saturday as Chelsea finally stopped a rot that has seen them turn a four-point lead in the Premier League into a 10-point deficit.

Lampard told Chelsea TV: “We can’t be content with being 10 points behind the leaders – we need to close that gap.

“It’s certainly not over, we all know that. It’s only pre-Christmas so it can’t be over but we have given ourselves a very tough task which we did again last year, when we fell away and never recovered.”

Before then, Chelsea’s focus will be on winning the Club World Cup and they trained again today having seemingly fully adjusted to the time difference ahead of Thursday’s semi-final with Monterrey.