TORONTO, Canada - No.8 seed Serena Williams ended the dream run of Czech qualifier Marie Bouzkova in the semifinals of the Rogers Cup on Saturday, advancing to her fifth career final on Canadian soil.

The 23-time major champion lost serve three times in the opening set against the 21-year-old World No.91, who was looking to win her seventh straight match in Toronto and advance to her first WTA final, but rallied to win in three sets, 1-6, 6-3, 6-3. 

The World No.91, in uncharted territory, hung tough over of the course of nearly two hours, before the No.8 seed won four straight games to force a decider, and stamped her authority in the decider by winning four of the first five games. 

After making 18 unforced errors in the first set, Williams ended with a total of 36 winners to 38 unforced, and also served 11 aces to seal her 500th career WTA match win on hard courts.

"I just needed to be more consistent and not make so many errors and just mentally be ready to hit a thousand balls if I needed to," Williams said after the match.

"In the first set, I was going for a little too much, so I just had to just play a different game. That was really important for me was to just change it up and move it around and not be so predictable.

"It's a good lesson for me in the future, as well, more than anything. I definitely feel more grooved in, but at the same time I feel like -- you know, I feel good still. I feel really good. I've been doing a lot of training and all the right things, so we'll see how I feel tomorrow."

Williams advances to a final at a WTA event, outside of the four Grand Slams, for the first time in over three years, since winning the Internazionali BNL d'Italia over compatriot Madison Keys in May of the 2016 season.

"I haven't had this in a really long time. We'll see what happens. You know, it's definitely different for me. I knew coming into the tournament," Williams said. "When they told me Wednesday, I was like, 'Oh, my God. Are you sure?' 

"When you're that young, everything is so fun. I mean, everything is still fun, but everything is new and everything is a different challenge and there's not a ton of pressure, so it's just different, and that's always just really always a plus."

The American, a three-time champion in Toronto, will next face another rising star in home hope Bianca Andreescu, who advanced to her third final of the season with a tight two-set victory over another American in Sofia Kenin in Saturday's first semifinal.

"She hasn't played a lot, but she's won a lot. So she's done really well. Yeah, I haven't either. But now we both are starting to get healthy and play a little bit more," Williams said.

"The crowd will obviously be for her. I definitely would too, but it's really not about that. It's just about going out there and playing your great tennis. Luckily, I've had some tough crowds in my career, so hopefully I will be used to it."