After winning the first set to love, Pegula cruised through to the quarter finals despite a mini-resurgence from qualifier Niemeier. "I knew I was going to be a little nervous and things were going to be weird," Pegula said post-match.
"But then I came out playing really well and I don’t think she was playing her best.
"I know she’s the type of player where she can make some really good shots. She has a lot of power and she’s super crafty. I definitely thought if I gave her any chance, she was going to try to make a run there at the end."
Before the tournament began it was announced Pegula would be working with Mark Knowles and Mark Merklein after she parted ways with long-time coach David Witt.
The number one seed will face Anna Blinkova or Dayana Yastremska in the last eight.
Perfection to end it 💯
In her first match since the Australian Open, top seed @jpegula gets underway in San Diego with a straight-sets win over Niemeier!
#SanDiegoOpen