Brandon Maurer has righted the ship quickly after a dreadful first couple starts and, in doing so, has validated why the Mariners gave him a rotation spot in the first place. But just because he'll be sticking around doesn't mean you should rush to add him in Fantasy.
He hasn't contributed much in the way of strikeouts, and he has yet to pitch seven innings in a game. As a 22-year-old making the leap from Double-A after pitching only 137 2/3 innings there last year, he probably won't do much of either.
In AL-only leagues, you can live without that stuff, but a competent mixed-league starting pitcher needs to contribute at least one or the other. If given the choice, I'd take Jeremy Guthrie, Bartolo Colon or even a down-the-road option like Drew Smyly or Dan Straily over Maurer.