Firmino had been a doubt for the encounter at Dean Court after picking up a knock last weekend, while Lallana has been out since suffering a groin injury on injury duty with England last month.
"Adam [has been] training since Thursday," Klopp told reporters at his pre-match presser today. "It went good, but of course we need to see how he reacts [to] the intensity of the training. Yesterday it was quite intense for him I think, but all good. Having him back is good.
"Roberto trained yesterday too. [There is] still a little bit of pain. It's painful but not that serious. When you can deal with the pain it's fine. He's quite a tough guy and he came through the session yesterday so we have to see how he reacts."