Stubbs teamed up with the 23-time Grand Slam champion before Williams' last ever major appearance in New York at the end of last summer.
Part of Stubbs' training involved getting Serena completing practice sessions with several different players in the run-up to the final Grand Slam of the year. While Williams put in promising performances against some of the world's top players - including Ons Jabeur, Maria Sakkari and Sofia Kenin - she was comprehensively outplayed Alycia Parks.
During the Rennae Stubbs Tennis Podcast, the Australian remembered how Parks outclassed the veteran Serena.
Serena was having a bad day. She was not in a great mood at all. Little did I know her dog had passed away that day. So, Serena's having a bad day, but she is getting spanked by Alycia. She was acing at 120 miles an hour, t-serves out wide. I'm like 'what the f***.
I'm like, first of all, why would you get this girl to practice with Serena. She loves Serena, clearly her idol but she's gone out here and she's having the best time, serving up court, she's like this is great, no pressure on me.
Both Williams and Stubbs have recalled how impressed they were with the powerful display of such a young talent.
I think Serena knew of her as well but, we were like, this girl's so good. She is literally pounding the ball. I mean, how do this girl lose? So, then she does great at the end of last year, won a couple of small, like Challenger events, back-to-back and got her ranking high enough.
Alycia Parks is one to watch this year, as her career starts to take off. She reached a career-high ranking of World No. 51 on the tour after she clinched her maiden WTA title at the Lyon Open on Sunday.