Yes. There aren't that many players around that won 5 CL (and are willing to entertain the move to the Saudi league) and collecting as many of them looks like one of Saudi's goals (Cristiano & Benzema are already there, they've offered contracts to Kroos, Modrić and, I believe, Varane...).
Also, "not even Premier League quality" is still more than good enough (in his case) for their league, which itself is nowhere near Premier League quality. Casemiro still has those beautiful passes in his arsenal and he's a considerable threat at set pieces, his main issue is that he doesn't really have the mobility (nor the reaction speed) to keep up with top level football — when that level drops, like in the League Cup, he looks rejuvenated and surprisingly useful. It's very likely that he'll actually perform well there... because their league is embarrassingly bad but still.