Ratcliffe appeared to hand Amorim a three-year backing last week.
But ahead of today's clash at Liverpool, Keane warned Amorim: "I'm not so sure about that.
"It's all well and good getting the backing off the board, but results have to improve. You hope, of course, any manager is given time.
"Whether he will get three years to play with depends how they do over the next few months. They have picked up a little bit - with the new attacking players they look more of a goal threat.
"But the big test is games like today. Are they going to show their quality or are they going to grind a result out? There are still question marks away from home. Yeah, they have picked up, but coming to Liverpool is a huge test and there are still huge questions marks over this group."