The Irons secured their progress through second-half goals from substitutes Pablo Zabaleta and Pablo Fornals.
Moyes observed, “To be fair, I didn't think the wing-backs got forward well enough in the first half and I wanted to play three at the back because I wanted to see that we've got the flexibility if we think we have to go that way, we can do so, and I also thought it was a chance to see how we could perform.
“Some of it was good, some of it not so good, but at least I've got an idea and I'm just beginning to get to know some of the players and what they're capable of. Overall, I'd have liked it to have been much better and much easier, but it was never going to be that way here.
"It was always going to tough."