Perhaps inspired by her first Top 10 win two rounds earlier against World No.10 Andrea Petkovic, Tsurenko wasn't intimidated from the start against the No.7-ranked Bouchard, jumping out to a 5-3 lead and even getting to set point at 5-4. Bouchard snuck that first set out in a tie-break, though.
But Tsurenko wasn't done by any means - Bouchard served for the match at 5-4 in the second set but the Ukrainian dug out the set, and Bouchard even went up 4-1 in the third set but Tsurenko dug out of that too. In the end Tsurenko was just too tough for the No.6-seeded Canadian, 6-7(5), 7-5, 6-4.
"A lot of things didn't go my way today in terms of everything," Bouchard said. "I felt heavy out there. Legs slugging from the beginning of the match. I tried to get myself going, but it was kind of a struggle throughout the whole match. I just didn't feel I was myself at all in terms of how I was playing.
"It's a learning type match. It's a tough one to learn from, but that's what I have to do."
"She was really good at the beginning of the final set. She was playing really aggressive, so I didn't have a lot of time to make my own shots," Tsurenko told reporters afterwards. "But I just told myself to keep giving my best and keep fighting for every point, and it really worked for me in the end.
"Honestly, I love this tournament. I enjoy coming here every year and every match I play here."
Not only has Tsurenko collected the two biggest wins of her career at Indian Wells this fortnight, but she's now through to the very first Premier Mandatory-level quarterfinal of her career.
Awaiting her in that quarterfinal will be No.18 seed Jelena Jankovic, who pulled off an inspired comeback against No.31 seed and WTA Rising Star Belinda Bencic, rallying from 3-1 down in the third set - even facing a point to go down 4-1 in the third set - to sneak the match out, 6-3, 3-6, 6-3.
Jankovic had lost her only previous meeting with Bencic in the fourth round of last year's US Open.
"At the US Open I had my chances," Jankovic said. "I think I was up 5-3 first set and got tired physically. It was so humid and hot out there, and somehow I let down. Physically I couldn't keep up.
"But she's a very good player. She takes the ball early, places it and hits down the lines a lot."
Jankovic and Tsurenko will be playing against each other for the first time.
? WTA (@WTA) March 18, 2015