Chelsea's pre-season results may have been less than inspiring to date, but they pale to insignificance when compared to the nagging doubts about centre-forward Diego Costa's ability to maintain match fitness.
Saturday sees the Blues begin the defence of their Premier League title with a home game against Swansea, and they may have to manage without the services of their talismanic striker, who hobbled off early in the second half of last week's friendly against Barcelona in Washington and hasn't played since.
Jose Mourinho said after the Barca game that Costa "felt a little thing in his hamstring," but subsequently appeared confident that the Brazil-born Spain international player would make yesterday's Community Shield vs. Arsenal at Wembley.
In the end, Costa was forced to sit out, leaving a frustrated Mourinho to field questions about the ongoing injury issues his first-choice forward faces ahead of the big kickoff.
"Will Costa be fit for Swansea? I don't know," said Mourinho after seeing his shot-shy side lose 1-0 to the Gunners. "You think I'm lying, but I'm not. Two days ago he was ready to play, and yesterday he trained normal."
Blues supporters will no doubt be thinking it's Groundhog Day as they see, read and hear the news that Costa's brittle hamstrings are restricting his availability for selection once more.
Costa was the catalyst for Chelsea's title charge last season, with his goals and pugnacious approach to the game. He led the London club's line with aplomb last year, and, as was witnessed on Sunday, Mourinho's men are a watered-down proposition without him.
Loic Remy was afforded a start against the Gunners but failed to seize the initiative and make the most of Costa's absence. Caught offside an amateurish number of times, Remy's lackadaisical performance saw Mourinho replace him at halftime with summer loan signing Radamel Falcao.
The Colombia international's CV boasts goals galore from his halcyon days at Porto and Atletico Madrid, but he looked a spent force last season at Manchester United. On Sunday, despite Mourinho championing his skills when bringing him to the Bridge last month, he was anonymous in Wembley's wide-open spaces.
Mourinho's indication that he will start Falcao in Wednesday's friendly against Fiorentina suggests that Costa is being protected with the Swansea game in mind. If Falcao can make a statement of intent in his first game at the Bridge, Blues fans would breathe a huge sigh of relief.
Speaking in April, Mourinho was adamant that Costa's recurring hamstring problems could be resolved without needing to resort to the surgeon's scalpel. "We don't believe in operations," he said. "I always believe it is the last decision for every injury, we try to be conservative, to train, recover and work. We don't believe we'll go the surgery direction."
In light of more recent events, Mourinho might be wishing he had challenged Chelsea's medical team to provide a more detailed assessment of Costa. With no resolution in sight and the Blues' backup options looking less than convincing, it will be interesting to see if the London club make a decisive move for a reliable top-flight striker in the transfer market before the summer window closes on September 1st. But who?
It's been an uncharacteristically quiet transfer period for Chelsea, who have sat on the sidelines and watched while Liverpool snapped up the services of proven Premier League striker Christian Benteke and Manchester United allowed the excellent Robin van Persie to slip away to Turkey almost unnoticed.
Meanwhile, Manchester City bolstered their forward options by signing Raheem Sterling from the Anfield club. Chelsea were linked with him and Benteke, but Mourinho has thus far maintained he is satisfied with the strikers he has at his disposal.
Last year, a last-minute acquisition saw Remy sign from Queens Park Rangers and, should Mourinho review his options in the wake of Costa's latest setback, he may be tempted to return to the relegated Rs and secure the services of Charlie Austin, who is 26 and scored 18 Premier League goals last season.
If Costa were 100 percent fit, there would be no problem, but -- playing his usual cat-and-mouse games when pressed on the topic -- Mourinho suggested that was not the case.
"The next time you ask me about Costa's fitness, I prefer not to answer. Maybe yes, maybe no," he commented.
For the record, in two league matches against Swansea last season, Costa plundered five goals. Wrapped in cotton wool, he may yet feature on Saturday, but it wasn't so long ago that Mourinho risked him from the bench in a game against Stoke and exacerbated a hamstring injury.
Time will tell if Costa is set for another season punctuated by stints on the treatment table, but surely, with so much at stake, Mourinho must know he cannot afford to gamble, given the apparent shortcomings of his alternative strikers.