The United manager was forced into a triple change while Patrice Evra was also carrying a knock in the second half as the Reds ran out 3-1 victors in the capital.
The reorganisation led to Antonio Valencia switching to right-back and the home side made a fight of things in the second half after trailing by three goals inside 22 minutes.
"It was three injuries," confirmed Moyes to MUTV. "Actually, we had four with Patrice Evra taking a knock just before half-time. Jonny Evans' back seized up, Rafael has gone over on his ankle and Tom Cleverley had double vision.
"It's the first time I've ever had to make three [substitutions] at half-time. Sometimes, maybe the team in the past has not played well and I might have had to do it but it certainly wasn't because of that today - it was down to injuries. I just have to hope they are okay."
Moyes admitted the hosts enjoyed the better of the second half after being blown away in the first period.
"I've got to give Martin Jol's team credit as they came out well in the second half," he stated. "If you're losing, as a manager you want a reaction from the team and he got that.
"We had to weather it a little bit and they had a few chances. The changes we made disrupted it a bit as it's difficult to bring on three but I think Valencia played really, really well at right-back and might have been our best player in the second