Sacked by England a year ago and later released by county side Surrey, the 34-year-old Pietersen appeared to have severed any chance of returning to international cricket following the release of his controversial autobiography.
Pietersen berated a number of former team mates and ECB officials in his book, and national selector James Whitaker said late last year there was no way he would "ever get back into an England team".
But in an interview with the BBC, Graves refused to rule out Pietersen's return.
"The first thing he has to do if he wants to get back is start playing county cricket," Graves said. "The selectors and the coaches are not going to pick him if he's not playing, it's as simple as that.
"At the end of the day it's down to the selectors and coaches and what they feel is best for English cricket.
"They will make the decisions and I will support them when it comes to that decision."
Pietersen told British media he was excited about the development, but the ECB later issued a statement that appeared to pour cold water on the chances of his reinstatement.
"Colin Graves is correct. Nothing has changed -- only players who are playing consistent high-quality county cricket and who are seen as a positive influence will be selected for England,” the statement said.
The "positive influence" was interpreted by British media as an attempt to row back on Graves' comments.
"Positive influence claptrap proof that some at ECB can't tell which way wind is blowing," Daily Telegraph cricket writer Nick Hoult tweeted.
Pietersen has existing contracts in the Indian Premier League and Caribbean Premier League Twenty20 tournaments and was non-committal about forgoing them in a bid to restart his international career.
"To be honest it's only happened in the last three hours and I'm not going to hassle anyone yet. I'll have to go away and make a few decisions, speak to some people and see where my future lies," he told Sky Sports.
Lauded as one of the most damaging and feared stroke-players of his generation, South Africa-born Pietersen scored 8,181 runs in 104 test matches for England at an average of 47.28.
(Reporting By Tom Hayward; Additional reporting by Ian Ransom in Melbourne; Editing by Toby Davis and Peter Rutherford)
