Ramprakash, 39, has been in terrific form in county cricket in recent seasons, and Miller hinted that the Surrey batsman could be called up.
'What we have to do as selectors is measure the quality of what they are putting in for domestic cricket and whether they can do it at international level,' Miller told Radio Five Live. 'There's a lot more pressure, it's a different game altogether.
'Test cricket is completely different from county, and the problem we have is deciding whether they can take their domestic form into the international arena. That's always been the case and always will be.'
When asked whether Ramprakash - who averaged 27.32 in his 52 Tests - would be looked at again, Miller replied: 'I'm not ruling anybody out. We'll have a look at it. There's an option. He's not retired from international cricket.'
Miller was also forced to defend the decision to omit Andrew Flintoff for the fourth Test, insisting it was right to put the advice of England's medical team ahead of the all-rounder's wishes.
Flintoff's agent claimed the 31-year-old Lancasterian had told England's selectors that he was prepared to play through the pain barrier, but the offer was rejected.
Flintoff has recurring knee problem and failed to convince the medical team of his ability to make it through the Test.