Diego Costa has turned into a pale imitation of the player who took the Premier League by storm last year and Chelsea must get him firing on all cylinders again to have any hope of salvaging their wretched season.
The 27-year-old striker could scarcely have believed his luck when he discovered last week that he had been recalled to Spain's squad for the friendlies with England in Alicante on Friday and Belgium in Brussels four days later.
He has scored only three times in 15 appearances for his club this season and the swashbuckling, battering ram of a centre forward who notched 20 league goals for the champions last term appears but a distant memory.
Chelsea fans, already mystified by their team's dramatic loss of form, are now wondering what has happened to Diego Costa.
Although the Londoners slumped to their third straight league defeat at Stoke City on Saturday, they produced a much-improved performance that suggested some key players are beginning to find form after a torrid start to the campaign.
Eden Hazard, the 2014-15 Premier League Player of the Year, again showed the tricky, ball-playing skills that tormented defences last season but more often than not, Chelsea's attacks petered out when the ball went to Costa.
Former Newcastle United target man Alan Shearer, a lethal international striker for England in his prime, said the temperamental Costa could learn a lot from Leicester City's red-hot marksman Jamie Vardy.
Vardy has netted in each of his last nine league appearances and will equal the 2003 record of former Manchester United and Netherlands striker Ruud van Nistelrooy if he scores in Leicester's next game at Newcastle on Nov. 21.
"Right now one (Vardy) looks full of energy while the other (Costa) is barely mobile," said Shearer.
"I studied Chelsea's performance on Saturday and actually thought they played as well as they have done for some time.
What frustrated me about Costa was the lack of trouble he gave Stoke's back four."
Shearer, who scored 30 goals in 63 matches for England, bemoaned Costa's lack of movement.
"Costa is constantly coming towards the ball now whereas you look at Vardy and he is always looking to run in behind the back four," he said.
"If you have Costa's ability there is only one place you should be, up front, facing defenders and running on to through balls."
Costa looks to be spending more time winding up opposition defenders than getting into the penalty box and if his barren run in front of goal continues, Chelsea may have little option but to seek a replacement in the January transfer window.
Jose Mourinho has received constant criticism for a remarkable slump in form that has seen Chelsea slump to fifth from bottom with 11 points from 12 league matches.
For someone who has shown little patience with managers in the past, owner Roman Abramovich appears keen to give Stamford Bridge hero Mourinho every chance to pull his team round.
The Portuguese will now be keeping his fingers crossed that Costa can get back on the goal trail with Spain over the next few days.