Klopp has been wrestling with an injury crisis in recent weeks that has sidelined several key players and forced him to turn to the club's academy to plug the holes.
Diogo Jota, Trent Alexander-Arnold, goalkeeper Alisson, Curtis Jones, Salah, Nunez and Szoboszlai all missed last Sunday's League Cup final win over Chelsea along with a number of longer-term absentees.
Diaz then sat out Wednesday's FA Cup win over Southampton but is fine to face Forest - along with midfielder Alexis Mac Allister, who has been ill.
"(Diaz) is fine and Macca (Alexis Mac Allister) is fine," Klopp told reporters on Friday.
"Darwin and Dom trained yesterday with the team so we will see how they react," the Liverpool manager added.
Salah has not featured for the Premier League leaders since their visit to Brentford on February 17th when he made a brief return after suffering an injury at the Africa Cup of Nations, but he could be in contention for next Sunday's game against title rivals Manchester City.
"I don't think Mo (Salah) is too far off. He will not feature tomorrow... I think next week, any point, it's possible."
Midfielder Wataru Endo and left-back Andy Robertson also both missed the midweek win over Southampton but are set to train with the team on Friday. Mac Allister and Robertson were both briefly sick with the same illness, Klopp said.
Liverpool's youngsters have stepped up to the plate in the absence of the established starters with 18-year-olds Jayden Danns and Lewis Koumas scoring their first goals for the senior team in Wednesday's 3-0 FA Cup win over Championship side Southampton.
Klopp said it was his job to protect the youngsters from the spotlight.
"I know that they are not ready for it... it was wonderful, they deserve it, of course, the spotlight that night... but now it's about dealing with the challenges coming up," he said.
The manager said Liverpool were under pressure to win every match to stay ahead in the title race, a situation similar to 17th-placed Forest who are fighting to stay clear of the relegation zone.
"We are only one point above Man City and two above Arsenal but that means nothing," he said.
"Nottingham is a great place to play but a difficult one. The situation they are in is a similar one to us, they need to win games to reach their target as much as we can," he added.
Forest, with 24 points, are four points above the relegation zone.
