Jurgen Klopp says that the defender has been training well following a back problem, while the ex-Gladbach star is making progress on a knock suffered on Saturday
The centre-back sustained a back injury during his side's 2-1 defeat to Napoli in the Champions League last week, while Reus picked up a knock in the 1-1 draw at Nurnberg on Saturday and was withdrawn at half-time.
However, Klopp says that Hummels has been training well, although he is slightly less optimistic on the former Borussia Monchengladbach forward's progress.
"Mats made a good impression in training," the 46-year-old told a press conference.
"Marco, meanwhile, is getting better. However, he's still far from being good."
Meanwhile, Klopp called for his men to focus on what he expects to be a difficult encounter at the Allianz Arena.
"I'm looking forward to the match. It's a difficult, yet appealing tie," he continued.
"We are warned. I will analyse the opponent, then we will make our conclusions."
Tuesday's clash with 1860 Munich kicks off at 18:00BST.