The pair both withdrew from international duty earlier this week due to knocks, with Clyne revealed to having carried a knee problem through recent games.
Lovren, meanwhile, complained of a groin issue after the Reds' 2-1 Premier League win over Swansea City last Saturday.
But there is less optimistic news on Adam Lallana, who went off in the same game after less than half-an-hour with a similar groin injury and is touch-and-go for the mouthwatering United clash at Anfield.
Lallana - one of the nominees for the Premier League's Player of the Month for September - had to withdraw from England duty and is believed to have been undergoing treatment at Melwood since.
Lallana fighting to be fit for United tie
The midfielder, one of Jürgen Klopp's best players so far this season, and Clyne will miss the Three Lions' 2018 World Cup qualifiers against Malta and Slovenia, in which teammates Jordan Henderson and Daniel Sturridge will hope to feature under interim manager Gareth Southgate.
Lovren's groin problem meant he had to declare himself unavailable for Croatia's World Cup qualifiers with Kosovo and Finland, although Klopp and co. are hopeful the centre-back's injury is less severe than Lallana's.
The Reds' No.20 has yet to be ruled out of the United game on October 17, affording him as much time as possible to put himself into contention, but the club are keeping an eye on his fitness.
It has also been revealed that everpresent right-back Clyne has been playing through the pain of a knee injury recently, but the two-week break now allowing a welcome period for the former Southampton man to rest and recover.
The trio are a number of first-team players to have remained on Merseyside for the next fortnight, with Germany duo Emre Can and Loris Karius, centre-back Joel Matip and the retired James Milner among those who will stay and train with Liverpool.
Coutinho in line for back-to-back Brazil caps
But Klopp could be forced to contend with the late returns of Brazil pairing Philippe Coutinho and Roberto Firmino, both of whom are in Tite's squad for South American World Cup qualification clashes with Bolivia and Venezuela.
The Selecao manager's recent praise of Coutinho suggested that he might feature in both of their games, with the second a 1:30am kick-off next Wednesday.
With any return to Merseyside unlikely to come until Thursday at the very earliest, Coutinho could be spared a starting role if he doesn't get sufficient training under his belt beforehand.
The 24-year-old playmaker, who has four goals and two assists in all competitions so far this term, only made the bench after the last international break.
Then, Liverpool had to make special arrangements to ensure Coutinho returned on Thursday for their Saturday evening showdown with Leicester City - which the Reds won 4-1 at Anfield.
However, with Liverpool locking horns with their old rivals United on a Monday night,Coutinho and Firmino do have extra time to get back into training with their club teammates this time around.