The former Kaizer Chiefs defenders arrived at Usuthu last week as the club looks to beef up their squad to form a solid team to compete.
Vukuzic speaking during a media briefing ahead of their Telkom Knockout opener away to Mamelodi Sundowns confirmed that Booysen has been signed and Masilela still needs extra assessment.
"They are not trialists, they came here to train with us, not to trial. They are well-experienced players so we wanted to check on the situation with them and also for them to understand the club," Vukusic explained.
"Mario I think definitely will be our player, with Tsepo we need a little bit more time because he hasn't played for a long time. He's responding very well and I'm happy about that but he needs maybe two to three weeks and then we will see on whether he will be signed."
The Slovakian then revealed that Booysen could make his debut on Sunday against Sundowns.
"It's possible that he will play because he is fit. We just need to do another medical test then we will decide from there."