Young tennis players being somewhat afraid to interact with seasoned professionals isn't anything new for tennis players and we've seen many instances of that in the past. Borna Coric had his moments with Serena Williams as revealed by Williams herself who described him as quite shy and reserved:
"I always saw Borna on tour. I think, in 2015, I was in Australia and he was always in the gym. I always joked with him that he didn't know I existed. So he finally realized that I exist."
Coric then jokingly said:
"I was a little scared because, on the court, she can get a little bit grumpy sometimes. I wanted to say hi, but then I was like maybe she's grumpy, I'm not sure if I should say hi or not."