By Matt Cronin, special to EmiratesUSOpenSeries.com

STANFORD, Calif. -- Coco Vandeweghe remembers the first time she came to the Bank of the West Classic, when she showed up to play qualifying as a 15-year-old and didn’t realize that her ranking was too low and she needed a wild card to get in.
 
She didn’t receive one but still got to practice with a woman who had just come off her first Grand Slam final at 2007 Wimbledon -- France’s Marion Bartoli.
 
"She crushed the daylights out of the ball," said Vandeweghe, who on Friday reached her first WTA main-draw semifinal with a 6-4, 6-4 win over Poland’s Urszula Radwanska. "I was like, ‘Oh my goodness.’ I never had anyone rip apart my serve like that. She went to town on it. But it was still awesome. Practicing with a top-10 player was totally cool – it still is. I remember the first time I hit with Lindsay Davenport, I said, ‘Wow I’m hitting with my idol.’
 
The 20-year-old Vandeweghe has shown flashes of brilliance before, but she has never been as consistent as she has been during the past month. Standing 6-foot-1 and blessed with athletic genes (her mother Tauna was an Olympic swimmer, and her grandfather Ernie and Uncle Kiki were both NBA standouts), she cuts an imposing figure, but her results have been up and down, largely due to inconsistent play from inside the baseline and during her return games.
 
Part of that had to due with the fact that she was still learning to play, and another part of it has to do with the fact that she didn’t have her footwork quite down yet.
 
She’s now focusing on getting her feet moving before points begin, and she has also decided that it’s very important to be steadier. Her coach of the past year, former top-15 player Jan-Michael Gambill, has insisted that she keep the ball in the court longer. And when she doesn’t in practice, she pays for it.
 
"The biggest change has been the number of balls that I’m allowed to miss," she said. "Before in practice, if I missed a feed, I’d just get another ball. Jan-Michael says, ‘What’s up with that?’ Do sprints or something else awful. He wants me to be an eight- to nine-ball player in rallies. He says, 'If a girl can play 10 to 12 balls with you with the pace and depth of your shots, OK, but I don’t think many girls can.'"
 
Gambill also has his student stand at the net and crushes groundstrokes at her because he wants her to improve her reflexes, as he believes she’s the best volleyer around.
 
"He tries to peg me, but he only has once, and that was on a let cord, so I consider that a technicality," she said with a laugh.
 
Vandeweghe got into the Bank of the West as a lucky loser and then pulled off three wins, including besting former No. 1 Jelena Jankovic, who has handled her easily in the past, in the second round. She called that win one that she’ll remember forever, but she’ll also recall the win over Radwanska because Gambill is playing World TeamTennis this week and her mother was granted the coaching badge.
 
The first time she called her mother down to the court, her mom told her that she wanted to hear "squeaky" feet and to make sure that she played at her rapid pace all the time and not get lulled into slower rallies. The second time she called her down it was during a bathroom break for Radwanska.
 
"I just didn’t want to sit by myself and get bored," Vandeweghe said with a laugh.
 
This has not been an easy year for Vandeweghe, who suffered an injury early in the year and fell to No. 169 in the rankings in March, well off her career-high of No. 89 in 2011. But she made a big effort on the clay, playing USTA Futures and Challengers, and while she didn’t find a lot of success on the surface, she felt like she was gradually improving.
 
Then she put her feet on the lawns at the Nottingham Challenger,  qualified and reached the final, losing to none other than Radwanska. With the rain, she ended up playing eight matches in seven days and was pleased with how she competed.
 
"I was down 5-0 in the tiebreaker against Anna Tatishvili, and on grass when it is like that, you are pretty much done, but I pulled it out."
 
She then qualified for Wimbledon, coming back from 3-5 down in the third set of her final match. In her first-round main-draw match, she didn’t play well in a straight-sets loss to Roland Garros finalist Sara Errani,  but there was a light moment. Well, sort of.
 
The  match had been suspended for darkness at 6-1, 5-3 for Errani, with Vandeweghe serving at match point down. When they came back the next day, Coco double faulted to lose the match. They both laughed at the net.
 
"I was hoping I wouldn’t double fault, but I wasn’t going to go out there and serve like I did the night before," she said. "Jan-Michael said to me later, ‘When I was warming you up, I didn’t think you’d go out there and double fault on the first point.’ I said, 'Thanks, it’s not like I planned it.'"
 
With her semifinal appearance  at Stanford, Vandeweghe, who is currently ranked No. 120, is sure to crack the top 95 next week, which will guarantee her a spot in the main draw of the US Open, which she says is a weight off her shoulders.
 
But she has bigger goals and, on Saturday, will have to confront 2009 US Open semifinalist Yanina Wickmayer. If she wins that match, she might have to face 14-time Grand Slam champion Serena Williams in the final.
 
But win or lose, she’s on the upswing.
 
"I’ve put my nose to the grindstone in the work, and I knew eventually it would turn into results," she said.