Kvitova came out swinging for the fances, reeling off four of the first five games of the match - and hitting 13 winners to just three unforced errors along the way. That momentum would dissipate as quickly as it came though, and Kerber clawed back from 4-1 down to take the set in a tie-break.
During that second half of the first set, Kvitova cooled off with eight winners to 13 unforced errors.
"She started playing more aggressively and I started making easy mistakes - that was the difference in the first set," Kvitova said. "But I just kept fighting until the end, and I started playing a lot better."
Indeed she did - across the second and third sets she put together a +10 differential of 26 winners to 16 unforced errors, and at the end of the day Kerber just couldn't keep up at the most crucial of times - the No.5-seeded Kvitova scored a come-from-behind 67(3) 62 63 win over the No.8-seeded Kerber.
"I'm a little bit tired right now. It was a really tough match from both sides," Kvitova said. "She played so well today, but I'm happy with how I played and I'm really happy to be in the semifinals again."
A few other stats jump out - Kvitova won 30 of 38 points at net and six of her nine break points. She is now 31-4 on indoor hardcourts since the start of 2011 and a hefty 8-1 against lefties this year (the only loss to a fellow left-hander came in the second round of the Australian Open to Laura Robson).
But the Czech has to refocus now, as she has a one day turnaround before the semifinals, where she will face No.4 seed Li Na. Their history couldn't be closer - Li and Kvitova are tied in their career head-to-head series, 3-3, going 1-1 against each other in 2011, 1-1 in 2012 and, of course, 1-1 in 2013.
Their last meeting came in the quarterfinals of Beijing just a matter of weeks ago, with Kvitova taking Li down in front of her home crowd in a tough three-setter, 46 62 64 (read more about that here).
"She's a good friend of mine," Kvitova said. "It's always good to play against her and it's always a tough match. We just played three sets in Beijing. But right now I'm just really happy about my win today - I really wanted to get to the semifinals this week. But of course it's going to be tough tomorrow."
This is just the third time in the last 21 years that a lefty has reached the semifinals of this event. Since 1992, only Monica Seles (2000) and Kvitova (2011 and now 2013) have made the semis or better here.