But Swansea have fingers crossed that Michu, Michel Vorm and Jose Canas could all play some part in a potentially critical clash with Cardiff City.
Swansea return to training this morning having had two days off since an awful display at Upton Park.
And the news that Shelvey, one of the few scrappers in Michael Laudrup's squad, looks set to miss the Cardiff game will do nothing to lighten the mood.
Shelvey has been struggling with hamstring issues for a number of weeks.
He missed the FA Cup win at Birmingham ten days ago and then limped out of the West Ham reverse.
Swansea are still assessing the extent of Shelvey's injury, but the initial feeling is that he has little chance of featuring against the Bluebirds.
And that is a heavy blow given that the £5 million former Liverpool man has been one of their better performers during their recent barren run.
Shelvey's probable absence may increase the temptation to plunge Michu straight back into action — although Laudrup has insisted he will not rush the Spanish international back.
Michu is due to return to full training this week having undergone ankle surgery.
The return of last season's 22-goal top-scorer could be key for Swansea as they bid to pull clear of relegation danger.
But Laudrup has stressed that Swansea need to be careful with Michu — and suggested last week that there was no chance of the 27-year-old being fit to start against Cardiff.
However, just having Michu back in the matchday 18 would be a huge lift for a Swansea squad who are still licking their wounds after a passionless performance against West Ham.
Like Michu, Vorm has not played since the 1-1 draw at Norwich in mid-December having had an operation.
His return would also be a significant boost for Swansea, for the Dutch international keeper is a big presence between the posts.
Canas's possible comeback may be regarded as less significant — although it would be timely given Shelvey's situation.
The holding midfielder has not played since the league defeat at Manchester United on January 11 after damaging ankle ligaments, but is on course for Cardiff having returned to full training at the end of last week.