London - Chelsea kick off their Premier League title defence against Swansea on Saturday fretting that Diego Costa's injury problems could hamper their bid to remain England's pre-eminent force.
Costa's 20 goals in 26 league appearances were crucial as Jose Mourinho's side took an early grip on last season's title race that they never relinquished.
But concerns about the Spain striker's fitness became a recurring theme throughout the campaign and it frequently took the brilliance of Eden Hazard to make up for the side's diminished attacking threat whenever Costa was absent.
And the sight of Costa limping out of a recent friendly with Barcelona followed by his enforced absence from last weekend's Community Shield prompted fresh concerns that the former Atletico Madrid star's problems have not yet gone away.
Chelsea manager Jose Mourinho has stuck by his policy of operating with a squad that includes just three strikers, with Radamel Falcao arriving on loan from Monaco to join Loic Remy as back-up to Costa after Didier Drogba moved to Major League Soccer's Montreal Impact.
The evidence of pre-season, however, has been that Chelsea's attacking options appear under-powered compared to their main rivals and while Mourinho has not ruled out the possibility of Costa facing Swansea when the champions return to action at Stamford Bridge, the chances appear slim.
Mourinho's team have failed to win any of their warm-up games in 90 minutes and meet Swansea after suffering successive 1-0 defeats, first to Arsenal at Wembley on Sunday and then at home to Fiorentina on Wednesday.
And while the usual caveats about friendly matches apply, Chelsea have looked alarmingly blunt in front of goal, with Falcao - who endured a miserable loan spell at Manchester United last season - showing few signs of returning to his best.