Ferrari and Vettel confirmed on Tuesday that the two would not be continuing their partnership beyond the current year, and with the door now closed at McLaren, Vettel's future remains unknown.
However, Brown states that McLaren knew it would either end up with Ricciardo or Sainz for 2021, and there were no other options explored outside of that.
“Obviously Seb is an awesome driver and a four-time champion,” Brown told Sky F1. “But I think we were pretty far down the path in the off-season and knew we would either land with Daniel or Carlos.
“We never really entertained anyone beyond that and especially with Seb's late breaking news - we were pretty far down the path at that point.”
McLaren attempted to sign Ricciardo for 2019 before the Australian opted to join Renault on a two-year deal.
However, a tough maiden campaign at Renault left Ricciardo reassessing his options, with Brown admitting that a lot of positive change has occurred in the last 12 months at McLaren which has encouraged Ricciardo.
“Getting a grand prix winner like Daniel is definitely a sign that we're going in the right direction. He believes in that,” Brown said.
“We went after him a couple of years ago before he made the decision ot to join us. I've talked to him about it since. He said 'You were coming off a pretty poor season', which was putting it politely.
“But also, there was a lot of 'this is what we're going to do' to improve the team. I hadn't yet brought in Andreas Seidl or James Key or restructure the leadership team. So there were a lot of promises and coming off such a bad season, I could see why he would go 'Let's see how this plays out'.
“And now it's played out, I've liked how it's played out and now he's seeing with the changes we've made, the leadership Andreas has brought and the backing we have from shareholders, going to the Mercedes engines, we're a team on the move.
“I think he's going to help us get to the next level.”
Bahrain International Circuit - Winter testing