Nunez recently received treatment for a cut on his ankle at the Reds' AXA Training Centre after withdrawing from the Uruguay squad before the international break, but the striker could be in contention to feature against the Citizens.
As for Diaz, the Colombian winger has been sidelined since October with a knee injury, but he has stepped up his recovery in first-team training this week and is another who may return to the matchday squad on Saturday.
Left-back Kostas Tsimikas will be assessed ahead of kickoff after sustaining a rib injury in Greece's goalless draw with Lithuania on Monday, while Thiago Alcantara (hip), Stefan Bajcetic (thigh) and Calvin Ramsay (knee) all remain in the treatment room.
Jurgen Klopp named four attackers in his starting lineup for the 1-0 defeat against Real Madrid in the Champions League last-16 just over two weeks ago, but the German will likely revert to a three-man attack and midfield on Saturday.
Should Nunez pass a late fitness test to start, Diogo Jota could be the unfortunate one to make way, with Mohamed Salah and Cody Gakpo - the latter of whom recovered from a virus to score in the Netherlands' 3-0 win over Gibraltar on Monday - set to retain their places in the first XI.
Jordan Henderson missed the trip to Real Madrid due to illness, but he played for England during the international break and is in contention to start in centre-midfield alongside Fabinho, while former Man City man James Milner will be hoping to keep his place ahead of Harvey Elliott and Naby Keita.
Klopp could stick with a back four of Trent Alexander-Arnold, Ibrahima Konate, Virgil van Dijk and Andrew Robertson, protecting goalkeeper Alisson Becker, although Joel Matip and Joe Gomez are options to start at centre-back.
Liverpool possible starting lineup: Alisson; Alexander-Arnold, Konate, Van Dijk, Robertson; Henderson, Fabinho, Elliott; Salah, Gakpo, Nunez