Chelsea are expecting to find out more on Sunday as to the severity of an injury suffered by star striker Joao Pedro.
Alonso did not specify the problem he was dealing with, confirming only that there was a build-up of fluid that meant they must wait before conducting further assessments.
Joao Pedro is expected to undergo a scan on Sunday, after which a fuller picture will emerge in terms of how much time he is set to miss.
Asked after the 2-0 defeat by Tottenham how bad the Brazilian’s injury was, Alonso said: “We don't know yet because he has a lot of fluid.
“He felt it yesterday and we need to wait probably until tomorrow to do the test and to know the whole situation and the whole seriousness of the injury. We will know soon enough.”
Star striker: Joao Pedro has thrived since joining Chelsea from Brighton last summer
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Chelsea will be desperately hoping that Joao Pedro’s latest injury is not serious, with the 25-year-old having scored five goals in seven appearances across all competitions so far this season - with three assists - to follow the 20 he hit in his first campaign in west London after a £60million transfer from Brighton last summer.
In the absence of Joao Pedro against Tottenham, Alonso made the surprise decision to start Morgan Rogers as a false nine and bring little-used summer signing Geovany Quenda into the attack, instead of striker Danny Welbeck or fan favourite Estevao.
It was a choice that did not pay off, with free-scoring Chelsea looking unusually sluggish and ineffective in attack before Cole Palmer was sent off late on amid a frustrating collapse that saw Spurs score twice through a Mike Penders own goal - on his first Premier League start in place of the injured Emi Martinez - and Mathys Tel’s fine individual effort.
As well as Joao Pedro and Martinez, Chelsea were still without the likes of Pep Chavarria, Jamie Gittens and Emmanuel Emegha for only their second home league defeat by rivals Tottenham in 36 years, while captain Reece James is a long-term absentee following knee surgery.