He told Sky Sports News: "It was a very good test, Preston are a big club. From our point of view I'm pleased with the clean sheet but think we can play better.
"No disrespect to Preston, but we are looking to create more, particularly in that second half.
"All three subs were injuries, we'll have to see how they settle down. But on reflection that was not a bad start in the end."
Striker Griffiths went closest to breaking the deadlock just before the break on a day of mixed fortunes for Wolves, but his effort was cleared off the line