The 24-year-old was making his first Aviva Premiership appearance since injuring his knee in the away clash against the same opponents last season.
"It was great to get a full game under my belt, but it was a long 80 minutes," Kruis told the club's official website.
"Most of the second rows at the club have played in 40 minute stints during pre-season so it was a tough 80, but I really enjoyed it out there. We got stuck in and stayed true to our game plan and it came good in the end.
"It's the beginning of the season, but we do expect a bit better from ourselves. We got the win, but we judge ourselves on performances so we know there's lots to work on going into the Harlequins game."
Saracens return to action when they face Harlequins at Twickenham on September 12.