Penguins fan here. Plotnikov came from Russia with high expectations, and fans and management expected him to play on a line with Malkin. When he played at the start of the season, he looked to be a very solid player but just wasn't capitalizing on any opportunities. He took too many penalties, but most of them were pretty bad calls. He isn't terribly fast, but he used his size to throw checks and battle for pucks, played responsibly, and got some good scoring chances. He still has some of the best possession stats of anyone on the team. The problem is that he has only 1 assist and didn't score a single goal. BUT, he usually played on the fourth line and didn't get very many minutes. Then he started being a regular scratch. Lots of fans have been angry/perplexed by this situation, unsure why he wasn't getting any chance to play and constantly being scratched in favor of new AHL call-ups.
Supposedly he expressed interest in wanting to go back to Russia, and was unhappy with how he was being used. I think this irked the coaches so that they decided just not to play Plotnikov at all. Its still unclear why he wasn't played, and it is also unclear at what point in time he first expressed his unhappiness with his situation. Coach Sullivan is really preaching "speed" with his players and how they play, and it could just be that Plotnikov wasn't fast enough.
Anyway, I really hope he gets a chance to actually play with you guys. I think he could be a solid bottom sixer, with top 6 potential.
Edit: Sorry, he has TWO assists, not one. Still, just look at his limited minutes played and keep in mind he was mostly on the fourth line. Then look at his advanced stats.