STANFORD, CA, USA -- Everything is clicking for CoCo Vandeweghe in her California return at the Bank of the West Classic.

The World No.24 has not come close to dropping a set en route to her first semifinal since the Australian Open in January, beating Ajla Tomljanovic, Nicole Gibbs, and No.4 seed Anastasia Pavlyuchenkova to set up a showdown against either Petra Kvitova or CiCi Bellis on Saturday. 

In five sets played, Vandeweghe has saved all six break points she's faced on her vaunted serve, and has yet to be broken.

"My feeling is that it's not like I'm getting crazy high percentages but I think my play off the ground has been very solid," she said. "I've been moving very well off the ground. 

"I don't feel like I'm playing off too many second serves consistently in a game, which helps me. If I'm playing off one or two second serves in a game that's okay, but any more than that then you start feeling [the pressure] yourself, that 'Gosh, I'm hitting second serves all the time, I need to get a first serve in'."

After a sudden split from coach Craig Kardon after the French Open, Vandeweghe has turned to 1987 Wimbledon champion Pat Cash on the coaching front. The pairing has been a success so far. After a first round hiccup in their first tournament tournament at the Ricoh Open, Vandeweghe went on to make back-to-back quarterfinals at the Aegon Classic and Wimbledon. 

The two had a solid week of training ahead of Stanford and everything seems to be gelling for Vandeweghe, who experienced a brief lull in her season after her outstanding run to the semifinals in Melbourne. She also revealed she has been working with a mental coach since Wimbledon.

"Mentally, it's going well," Vandeweghe said. "There's definitely some new things I'm implementing from Pat as far as the mental side of things. I've started to work with a mental coach so I think mentally I'm stronger than ever."

Earlier this year, a reporter asked Vandeweghe whether she had ever worked with a sports psychologist and whether she would consider it. The 25-year-old said she had worked with one for a brief time but did not feel it was for her.

She's still not sure of the long-term benefits, but she's willing to give it a try if it benefits her tennis.

"It's not a psychologist," Vandeweghe emphasized. "I still am not a fan of it. I told the mental coach this also. 'Listen, I'm not a fan of what you guys do.' He said, 'That's fine. You don't have to be as long as it works.' I was like, 'Prove me wrong'. I think that's what's good -- honesty is what works in a give and take relationship."

"I've literally talked to the guy twice. It's not like I'm calling him every day on the phone, which I would hate. That's probably why I don't have a boyfriend, because I don't have to talk to somebody every day on the phone," she said, laughing. "My mom is the only one that maybe gets me on the phone every day."

"But it's just routine. There's different checklists that I go through every day. There are things he's implemented, there are things Pat has implemented. It's a mix and match of everything."

Looking ahead to her semifinal in Stanford, Vandeweghe is aware of the challenge she's set to face. On one hand, it could be a pounding Kvitova, against whom she's 0-3. On the other it could be another ambitious California girl, in 18-year-old Bellis. 

"I can only really speak about Petra because I don't know CiCi at all really that well," Vandeweghe said. "I've never hit with her nor have I ever played against her. 

"Petra's a tough opponent for me. I don't think I've beaten her yet. A lefty is tricky, especially a lefty with power. I think it's going to be up to myself really. That's the only thing I can worry about, making sure I'm in the right mindframe when I'm out there and competing as hard as I can."