The Hammers were thumped 4-1 on Wednesday night.
Moyes said, "I was disappointed with the performance. I wasn't disappointed we improved in the second half.
"At 2-1 I felt we got ourselves back in it and in a way we went chasing it and we got picked off once or twice but Leicester played well tonight. We didn't play well and we had been doing OK, so that is disappointing.
"I knew January was going to be really, really tough. The Premier League at different times has brought shocks, we just have to make sure we bring one of those shocks in the games coming up."
On potential new signings, he added: "We do need players, we are short. We need the energy and fresh legs. If we can get it we will do but I can't guarantee that."