Fears regarding the length of Nathaniel Clyne's current injury lay-off have been exacerbated after the England right-back was omitted by Liverpool manager Jurgen Klopp from his squad for the group stages of the 2017-18 Champions League.
Clyne missed the majority of pre-season due to hamstring and back issues and has remained sidelined for the Reds' first five fixtures across all competitions, with seemingly no time frame in place for his eventual return.
The 26-year-old initially withdrew from international duty in May and was not considered for selection by England boss Gareth Southgate for the 2018 World Cup qualifying double-header against Malta and Slovakia.
With Clyne now ineligible to feature in European competition until February, when up to three new players can be registered before the round of 16, Liverpool's right-back options for home-and-away Group E meetings with Sevilla, Spartak Moscow and Maribor are young Trent Alexander-Arnold, the versatile Joe Gomez and Jon Flanagan.
Having been denied a big-money summer move to Barcelona, Philippe Coutinho is included in a Champions League squad that had to be submitted while the Spanish transfer window was still open for business on Friday (1 September). Liverpool firmly deny Blaugrana director Albert Soler's claims that they slapped a €200m (£183.8m, $238.1m) valuation on the disgruntled midfielder in the final hours before the deadline.
Like Clyne, Coutinho has yet to feature for Liverpool this season but was fit enough to come off the bench and net for Brazil during their victory over Ecuador in Porto Alegre. He will also be in contention to face Colombia on Tuesday night before travelling back to the United Kingdom, where he could make his first club appearance of the campaign at Manchester City.
Adam Lallana is also re-added to the squad that beat Hoffenheim 6-3 on aggregate in the Champions League play-off round as he continues to recover from a thigh strain suffered at the Audi Cup in early August. New signing Alex Oxlade-Chamberlain similarly makes the cut after completing his £35m switch from Arsenal last week.
However, out-of-favour winger Lazar Markovic and injury-plagued striker Danny Ings are both left out alongside Clyne. The former failed to secure a move away from Anfield over the summer despite a promising loan stint at Hull City, while the latter has been limited to Under-23 duty since returning from a second serious knee problem in as many years.