Not too hard when he's as big as half the field.
On a serious note, I am becoming a little irritated by Lutui's seemingly depreciating lack of self-discipline and regard for his own body (which many in the fitness/athletic world will say is your "temple"). We expect him to come to camp a little overweight, but 30-50lbs is completely inexcusable, especially for a player worth millions over. Doesn't matter if he's under contract, tendered or a free agent, he has to stay in shape to be productive. Even the Bengals, one of the leagues worst franchises, felt he was dismissible and didn't want to work with him. Lutui coming back to AZ was more a favor for him than a bargain for the Cardinals in the grand scheme of things.
Looking at him tonight, while he did have a nice pull as you described above, he was still a step slow all game long. Lutui was playing with the #4s at the end and didn't really stand out in pass pro or run blocking. A player who has been starting his entire career should look like a man amongst boys in that situation. And until he can get into game shape (which is going to be very difficult to do midseason), he's going to be watching the game from the sidelines.
All tonight's performance tells me is Deuce should make the team, but I wouldn't be surprised if he's either 2nd string or not dressed week 1.