Brinsden told the Resources Rising Stars conference in the Gold Coast yesterday that he often got asked why the company would want to divest part of its flagship asset.
He said one reason was cost: the combined capital costs for the stage two and three expansions would be "something like A$500 million".
The second part is about becoming more vertically integrated in the lithium supply chain.
"Relationships in this space are getting tighter and deeper," Brinsden said.
"The industry is generally getting more deeply integrated."
The strategic process is well underway, though Brinsden couldn't say too much.
"So far, so good," Brinsden said.
"I'm happy with the level of interest and am looking forward to what will unfold in the coming months."
Brinsden admitted it hadn't been a great period for lithium companies.
Pilbara shares peaked at $1.12 last year and have traded in a range of 62.5c and 83.5c so far this year.
Brinsden said Pilbara shares had held up better than its peers as its story was "real" in the sense it had built a mine, was in production and generating cash.
"The reality is if you're in Pilbara, you've done well because you haven't gone down as much as everyone else," he said.
Canaccord Genuity blamed US-China trade tensions, as well as global growth fears, for the recent weakness in lithium equities.
"The Global X Lithium & Battery Tech ETF was lower by 1.1% over the past week to close at US$24.62/share, the lowest level since the beginning of 2017," it reported this week.
Shares in Pilbara rose 1% yesterday to A68.7c.