Let's face it, no matter where you sit on the Keita issue (I personally think he's being bedded in very slowly & actually told to 'play safe' more than hiding, but I know you & others disagree, & I fully understand why FWIW, but this isn't the thread to reopen that debate), the fact is he isn't offering enough defensively or offensively at the moment to pick him for games against the top sides.
I don't think Chamberlain is impressing much either TBH, but, crucially, he's finding the back of the net, so if we were forced into choosing either in a big game, Chamberlain would make more sense.
Either one would be a huge gamble though, & midfield is the one area we very very rarely see Klopp take those types of risks, so I think there's little chance of that happening unless injuries/illnesses force Klopp into it.