Lallana suffered a groin injury midway through the first half of England’s 2-2 friendly draw with Spain on Friday night, heading straight down the tunnel at Wembley.
This suggested Lallana would miss the trip to St. Mary’s Stadium, with the 28-year-old set to undergo a scan at Melwood on Thursday.
Speaking ahead of the Reds’ 12th outing of the Premier League campaign, Klopp confirmed that the decision on Lallana’s inclusion “will be close,” but is hoping it isn’t a serious issue.
“With Adam we don’t know exactly. I spoke to him already, but we’ve not done a scan until now,” he told reporters.
“It will be close. Really. We don’t know, but hopefully not too serious. We have to wait.”
Lallana had a similar problem prior to the October international break, limping off the field in Liverpool’s 2-1 win away to Swansea City, forcing him out of England duty.
Then, he was given close to two weeks’ recovery, returning as a substitute in the Reds’ 0-0 draw with Manchester United on October 17, suggesting he is unlikely to make the starting lineup against the Saints.
However, Klopp continued to explain how, on the fitness front, “95 percent is good news,” with the majority of his squad now injury free and available for selection.
Ojo had missed three months with a back problem, while Gomez was out for a year with an ACL injury, with neither likely to feature against Southampton in Saturday’s 3pm kickoff (GMT).
Simon Mignolet, Ragnar Klavan, Nathaniel Clyne, Jordan Henderson, Georginio Wijnaldum, Marko Grujic, Sadio Mane, Daniel Sturridge and Divock Origi also returned without having suffered problems with their respective nations.