Williams rolls over Jankovic to reach semis
Serena Williams serves against Jelena Jankovic of Serbia during a match on day 7 of the Western & Southern Open at the Linder Family Center on August 15, 2014 in Cincinnati, Ohio - by Jonathan Moore
"She's beaten me several times, so I knew today I just had to be focused and do the best I could," said Williams, a 17-time Grand Slam champion who has never lifted the trophy in Cincinnati.
"She played some great points. I was just trying to not make many errors, stay focused and do the best that I could."
Williams will face either former world number one Caroline Wozniacki, who beat fourth-seeded Agnieszka Radwanska of Poland 6-4, 7-6 (7/5).
Second-seeded Simona Halep of Romania will get a chance to avenge her Roland Garros final loss to Maria Sharapova when she takes on the fifth-seeded Russian for a semi-final berth.
Sharapova has beaten Halep in all four of their meetings, although both of their matches this year have gone three sets, first in Madrid and again in the gripping French Open final that saw Sharapova claim her fifth major crown.
The winner of that match will play either ninth-seeded Ana Ivanovic or Ukrainian teenager Elina Svitolina, who vanquished Wimbledon champion Petra Kvitova in the second round.
Williams completed her win over Jankovic in less than an hour as she reached the last four without the loss of a set. The American fired seven aces and broke five times against the former number one.
Williams won 10 of 14 career matches against Jankovic, last losing to her in 2010. She has beaten the Serb five times in the past two seasons.
"I definitely felt pretty good about today, I felt better," said Williams. "My unforced errors are lower than they've been this year, so it's definitely going towards the right way.
"I don't think she played her best today and still she fought well. I was glad to have an opportunity to just get through that.
"I don't think I played great last week (semi-final loss on Montreal). I was just fighting to be in the tournament. I was mentally fighting really hard. I definitely feel like I'm playing better this week."