As was the case in September, the 25-year-old spent the two-week October break from club action on international duty with World Cup winners Argentina.
Mac Allister sat out of his country's 1-1 draw with Venezuela in CONMEBOL World Cup qualifying before starting the 6-0 thumping of Bolivia on Wednesday night.
The Reds star was subbed out of the contest to make room for Roma midfielder Leandro Paredes in the 66th minute, when Lionel Scaloni's troops were already three goals ahead in the match.
As a result, Mac Allister - alongside a number of other international stars for Liverpool - face a quick turnaround ahead of Sunday's battle with the Blues.
Liverpool suffer Mac Allister injury blow ahead of Chelsea test
With Sunday's clash with an in-form Chelsea side fast approaching, Liverpool have been dealt a fitness blow following the fortnight of international action.
Argentine Mac Allister was not present during first-team training at the Reds' AXA Training Centre on Friday, just two days before the visit of Enzo Maresca's Blues.
According to the Liverpool Echo, the 25-year-old was completing an individual session in the gym as he recovers from a multitude of fitness issues at the start of the term.
Mac Allister was subbed off at the half-time break during the 1-0 win over Crystal Palace prior to the international break due to a groin complaint.
As a result, the former Brighton & Hove Albion man is a major doubt to feature, let alone start, for Arne Slot's troops at Anfield on Sunday.
Another international also absent from Liverpool training
As well as Argentina's Mac Allister, Kostas Tsimikas was also absent from training on Friday after his involvement for high-flying Greece in UEFA Nations League B.
The left-back did not feature during his nation's historic 2-1 victory over England at Wembley on October 10 due to illness, meaning that former Norwich City man Dimitrios Giannoulis started in the backline.
Tsimikas mustered up a showing during the two-goal success against the Republic of Ireland on Sunday evening, however the Liverpool man only featured for eight minutes off the bench.
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