Before I comment on your argument re: Orlov vs Orpik, I need to understand something.
What "games sample" are you using for your argument, when comparing the 2?
Basically since Orlov came into the league in 2011-12 he has outperformed Orpik in every major metric, offensively and defensively. You can choose to ignore or downplay the stats if you want. I've already linked to articles showing that over the long run QOC and Zone Starts basically don't matter unless a player only starts in the offensive or defensive zone or if a player only faces top competition.
Since 2011-12 Orlov has started 28.1% of the time in the defensive zone, 37.5% of the time in the neutral zone, and 34.2% of the time in the offensive zone. Orpik's breakdown is 31.0% in the defensive zone, 40.5% in the neutral zone, and 28.4% in the offensive zone. So while Orpik has slightly more defensive zone starts, it's not as significant as people think.
With regards to quality of competition, Orpik's opponents have averaged 50.3% score-adjusted corsi over their careers, Orlov's opponents have averaged 49.8%. However with quality of teammates, Orpik's teammates have averaged 51.3% score-adjusted corsi (playing with Crosby, Letang, Malkin, Ovechkin, Backstrom) while Orlov's teammates have only averaged 49.8% (playing mostly without first line stars).
So basically the QOC is at BEST a wash and more likely actually favors Orlov because his teammates have been equal with the competition, whereas Orpik has played with teammates better than his competition on average.
So if you're saying Orpik playing slightly more zone-starts explains away his score-adjusted corsi being 8.2% worse than Orlov's (-3.8% vs. +4.4% since 2011-12), then I will disagree and point to the research showing that mild zone-start differences don't explain an 8% difference.
Ignoring stats for a second, Orpik doesn't pass the eye test either. Go back to Game 3 of the Islanders series. His inability to handle the puck near the crease cost the Capitals the game. He has been slower and slower recently and certainly won't be any faster when he returns from injury. How about all of the dumb penalties he takes in the name of "retribution"? How many times has he screened his own goalie? (I remember this happening all the time)
Orlov handled second pairing minutes when both Carlson and Orpik were injured and I'm pretty sure the Caps have kept on winning. He wasn't sheltered then because Ness and Chorney were sheltered.
Orlov deserves a chance to play top 4 minutes for an extended period to show what he has before Orpik does because Orlov has more recently shown he can handle those minutes, Orpik was a disaster early this season coming off injury and now he's coming off another injury. No reason to think a guy that old coming back from injury will be able to play at a high level, it's just not realistic.