The 16 year-old attacker is currently recovering from a major injury and has featured for United U18s this season.
Speaking on his podcast, Rooney Snr said: "The standard of English players has increased massively, I just think it's purely because they don't want to play number nine.
"The way the game is tactically. If you look worldwide there's not many number nines. So it's not just a problem in England, it's a problem throughout the world in number nines."
When the conversation turned to Kai playing as a striker, Rooney explained: "He's gone to the right. Left-footed, coming in off the right."
Dad has also said: "He has great coaches at Manchester United, so I take a stand off approach. I speak to him, but for me it's all about his mentality and his mindset, to make sure he keeps enjoying it - that's the main thing for me."