Klopp said Matip will definitely be ready for Arsenal. I'm 99% certain he is Klopp's #1 CB and he'll get a run out to prove his fitness vs. Barca or Mainz.
So Matip and Lovren or Matip and Ragnar ? I'd go with Ragnar.
Up front I agree with Brendan ... Sturridge should start though I'd expect to see Origi come on at some time.
I don't doubt who his longterm partnership is, but Klopp isn't stupid either, he's not going to watch Lovren play the whole of preseason, while Matip has had a stop/start preparation and then just throw him in anyway.