"We actually trained with him for a couple of weeks before he went back to Spain earlier in the season and it was clear to us all then that he's got loads of ability," said the Liverpool captain.
"You could see that he's hungry to do well, which is important, and he came across as a good lad as well. That's the type of player we want here – people who are good for team spirit and who'll also do a good job out on the pitch.
"I'm sure Mark is going to do that for us and like everyone, I'm looking forward to his arrival. We've all been following his progress at Real Sociedad via the Spanish football on television and he's been doing really well."