Reports initially speculated that the Spaniard would move to Mercedes in a straight swap with Hamilton, who will replace Sainz at Ferrari.
However, Mercedes appear committed to promoting their junior driver Kimi Andrea Antonelli to the team to replace Hamilton, despite his youth and inexperience in the sport.
When Sky Sports asked Vowles about their talks with Sainz, he remained cryptic, revealing very little.
However, the team boss did have time to take a jab at a rival F1 team when discussing tyre choices in FP1 with the commentary team.
“The two - don’t ask me what they’re called - AlphaTauri, Visa Cash App buy one get one free, went on the medium earlier, everyone else was on the hard,” Vowels said.