Moyes looks likely to stick with Adrian for Wednesday's game against Arsenal but a continued lack of first-team action will leave Hart in danger of losing out on a place in England's World Cup squad.
"I always have compassion for the players as well, that's why it wasn't an easy decision on Joe," Moyes told reporters. "But, ultimately, it's West Ham I have to get results for.
"He wasn't happy. I told him the reason why and that happens at clubs all over the country. It's a manager's job. When I came in, I said I will tell you straight, I wouldn't kid anybody."
West Ham are 18th in the table.
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"Joe is incredibly experienced. World Cup, Champions League football," Moyes said.
"So he's such an important player for us... he wants to play but I've got to do what's best for West Ham, pick the players I think will get us a result."
(Reporting by Aditi Prakash in Bengaluru, editing by Ed Osmond)
