He is in a minor dip. Thats why other players have been given the chance. But, in the last game vs Utrecht, his replacement (lazovic) didnt do well at all so Salomon might be starting for Feyenoord soon.
Before he got injured, Kalou's form did dip a little. He wasn't that good as at the start of the season. Also while Kalou was injured, his replacement Lazovic played a couple of good games and to add to that, when Kalou came on for us against Sporting last week as a sub, he looked well off the pace. I do expect though that Solomon will be back soon in the first team, given a week or two as Lazovics form hasn't been so good in the last 2 games either.
he's a striker with all the moves and dribbles, a bit like Nwanku Kanu, only Salomons more direct then Kanu. He's still very young though and so can have his off days here and there. However he really has it all to make it to the absolute top imo.
Just give him 2 more seasons at Feyenoord to ripen himself to then move on to a real top team in a top league and barring he goes mad or injures himself badly, I'm sure everyone in the world will know him.