I would guess tonight.
Does Samaras defend well when he plays on the left? You're going to want someone who'll track Lichtsteiner playing there.
Like everything else about Samaras... sometimes. He's one of those guys who can be awful but is always excellent in big games. On form he's probably best in that position, good on the counter attack and with his height and unpredictability (partly because
he doesn't know what he's doing half the time), difficult for wide players and full backs to deal with too. The left back Izaguirre has yet to get back to the fantastic form he had in his first season, but he should be quite good tonight.
That said, Sammy has been carrying an injury, so I am surprised and pleased he's playing... he might not play the full game tonight and we might use Forrest later on, the only other player we have who can really play the role he does for us, but who is only 21.
As I think about it we will probably start with him up front on his own with Hooper behind him, though. That's how we started against Spartak and in the Nou Camp. If it's not going well, easy to change it.