Chelsea are set to start the new season where the last one left off – with a minor injury crisis threatening to overshadow their Sunday Wembley date with Arsenal.
There were worries of a return of the hamstring problem, which limited Costa to just 24 Premier League appearances last campaign, and a feared broken nose picked up in a friendly against Barcelona that may cause problems for Cahill.
Boss Jose Mourinho was doing his best to put on a brave face, but was more relaxed about the defender – who he insisted would play against Arsenal in the season's traditional curtain-raiser.
He said: “Cahill has a chance of a broken nose, maybe yes, maybe no. If no, perfect. If yes, he will get a mask (Thursday) to be ready for Sunday.
"Diego felt a little thing in his hamstring. We believe it is just a feeling, no more than that, but we have to wait."
The Costa news was good and bad.
Sure, there are lingering concerns over the striker's notoriously precarious hamstring, but balanced by the positive the player knows when he is on the brink and can take evasive action.
Sunday's Wembley showpiece will be a chance for Mourinho to reveal just how far his pre-season has come after a stuttering start in New York where they lost a friendly to the Red Bulls.
Though lately reduced to the status of a friendly, Mourinho will accept nothing less than a win in the Shield – while hoping to continue a run of 14 matches against Arsene Wenger's side without defeat.
After that, there will be another 90 minutes on Wednesday night at Stamford Bridge against Fiorentina – with fans warned they could be affected by a planned London Underground strike.