Salo was working with Sirotkin as part of SMP's support programme last season; but Robert Kubica was announced as the man to replace the driver for Williams in 2019.
SMP, Sirotkin's backers claimed that they were the ones who 'pulled the plug' on their partnership and not the other way around - like the majority of the media believe.
Salo has supported these claims by SMP, stating that Sirotkin's sponsors were negotiating for a cut-price deal for the seat for 2019, after the dismal season Williams endured in 2018.
"It was pretty much up to Williams," Salo told Finnish outlet MTV. "Of course we wanted to lower the price a bit and get an assurance that Williams will get better. We did not reach a consensus.
"That's one of the reasons why I'm not worried that Sergey leaves (Williams)."
Salo was also talking about Sirotkin's future outside of F1; saying the Russian could make a return to the World Endurance Championship is a strong possibility for the driver.
"Sergey did a good season," Salo said. "He did a good job and the team liked him. His technical knowledge is astonishing and we have LMP (Le Mans prototype) cars that need a driver of Sergey's level."