Wijnaldum was substituted in the 17th minute of the 3-0 victory over the Slovenian side and manager Juergen Klopp said he had suffered an ankle injury.
Liverpool are already without Brazilian Philippe Coutinho (thigh) and Adam Lallana (thigh), while forward Sadio Mane remains sidelined as he recovers from a hamstring injury.
"At halftime I asked immediately and the ankle was already swollen. It’s probably not a good sign,” Klopp said of Wijnaldum, who looks unlikely to feature in Saturday's Premier League game at West Ham United.
"We saw a kick in the game and didn’t think it was too serious. Then it was swollen. We’re not sure if he twisted it or not. For sure, we have to make a scan...
"We missed three and then after Gini went off, four of maybe the most creative players in the league. It doesn't make your life easier because whatever you plan before the game the players have to do the job."
Coutinho is unlikely to be fit to face West Ham but defender Dejan Lovren, who also missed the Maribor game with a thigh injury, has a chance to play, Klopp said.
"It is different with Dejan," Klopp said. "It’s not the same problem Phil has and he is not out for that long a time, but Gini is out so maybe there will be a wonder or something like this and Phil is in. But I don’t think in this moment that he can play," he said.
Klopp said he was pleased with the way his team showed patience to break down a determined Maribor defence.
"We knew Maribor would play like this. That was no great surprise to us. But I'm pleased with our result and our reaction. It was not perfect from us, but we scored three goals, kept a clean sheet and are top of the group - perfect."
(Reporting by Simon Evans; Editing by Toby Davis)
