The fact Grace wasn't targeted more is due to the fact it can be hard to target wingers as much as a centre as the ball is going furthest it can to the edge but also because Grace didn't look out of place.
There was an occasion in the 2nd half where he was isolated on the blind side on the Saints line and managed to wrap his man up well. It went unnoticed but it was good defensive work. I guess the test will be when he has to make more collusion type tackles and his positioning is put under the microscope more, but given the low bar that Owens set it was a promising start.