The Reds manager says the full-back has accumulated a mixture of problems and has not been 100 per cent fit this term, while he was also hopeful over the transfer of Mohamed Salah
The 29-year-old England international has made 18 appearances for the Reds this season but has been criticised for his mixed form.
And his manager believes he has not been 100 per cent fit for the entire campaign, telling reporters: "Glen Johnson is sidelined indefinitely.
"Glen’s got a really bad ankle, and one or two other issues which haven’t allowed him to be 100% this season.
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Rodgers did have better news in the shape of a return for Jon Flanagan, who has missed the past few weeks with a hamstring injury.
He added: "Young Jon Flanagan is back and has been training really well."
With just eight days remaining in the transfer window, Rodgers said the Anfield club are keeping tabs on 'several targets', including Chelsea target Mohamed Salah.
He said: "We don’t need to bring any more defenders in. We just need to get some of our players back fit.
"We’re missing key players, but we’ve got to manage with what we’ve got. If we can bring anyone in, great, if not, we have what we have.
"We’ve looked at a number of players, but Salah is a talented player, but we’ll see what the window brings. We’re looking at several targets."
Rodgers also addressed the news of Lucas Leiva's injury. The Brazilian suffered a knee complaint in the 2-2 draw with Aston Villa and is expected to miss up to eight weeks, something Rodgers lamented.
"I’m disappointed for Lucas," Rodgers said. "He’s been very important for our squad this season. It’s put him out for a few months.
"Hopefully he’ll be back sooner rather than later. But in the mean time, it leaves us short of a really good player.
"Lucas has still got a great chance of being in the Brazil squad for the World Cup in the summer. That’s up to Scolari."