They're not D-men. Little different. But I generally agree.
If you're only going to play McBain 5 min anyway, I don't see Gravel as a downgrade, and it's not like McBain had playoff experience anyway (not before this). Assuming he's not hurt, mind you.
The 5 min thing is what's key for me. Gravel's upside is greater than McBain's but McBain is the safer commodity. If we're only gambling with 5 minutes of sheltered time (over 1 Min of McBain's TOI was on the PP) I think it is worth putting Gravel in.
He sure looked good in what time he has spent up IMO
Edit: From hockey futures
Talent Analysis
Gravel has very good skating for his size, including a good first step. His defensive positioning is exceptional and has become a real staple and defining factor to his game. He should have more points than he does given his puck skills and shot.
Future
Gravel is skating for re-located Kings' AHL affiliate Ontario in 2015-16 — appearing in four games with Los Angeles in February during his first NHL call-up — and is one of the Reign's top defensemen. In the first year of a two-year entry-level contract signed in June 2015, he is making headway at cracking what has been a strong blueline corps in Los Angeles. Gravel uses his size to advantage and can generate offense off the transition. He projects as a solid middle pairing defenseman.