Barbora Strycova has been battling more than just her opponents at the ASB Classic.
The Czech third seed has spent six hours on centre court through two matches at the Auckland tournament, requiring marathon efforts to qualify for the quarter-finals.
Throughout, Strycova has been battling sweltering conditions on centre court, but her toughest adversary so far has been the mental aspect of the game.
Twice, Strycova has had to recover from blowing golden opportunities. Against Sara Errani in the first round and Johanna Larsson in the second, Strycova had a chance to clinch straightforward two set victories, but couldn't close it out on either occasion.
Earlier in her career, those missed opportunities could have seen her lose her cool; such is the oscillating intensity that permeates through her game.
However, slowly but surely, the 31-year-old has learned to control her emotions, and it could be an indicator that she is set for her best showing in seven attempts at the Classic.
Strycova has made the quarters twice before, but has never made the final. That could change this year, with the most recent proof of her progression coming yesterday, where she had to overcome an unexpectedly long clash against Larsson.
Up 6-1, 5-2, Strycova looked set for an easy progression into the next round, but Larsson battled back, taking the second set in a tiebreaker.
However, Strycova refocused, regaining her cool, and eventually earning a 6-1, 6-7, 6-2 victory.
After taking three hours to beat Errani in the first round, Strycova hasn't made it easy, but on both occasions displayed a much improved mental fortitude and a calmer presence.
The refreshingly genuine Strycova was pleased with her resiliency.
"I'm happy I could refocus after the second set – it's not easy to. It shows that I work really hard – I can win these matches in really tough conditions."
Strycova still has her angry moments on court, bouncing rackets and smashing balls in frustration. The difference this time, is she can now channel that emotion into bouncing back to win crucial points.
"This is something I've worked on in the offseason a lot; I have my mental coaches as well so we work on these things. I was just sitting on the bench and just thinking about what I have to do, and focusing on myself," Strycova explained.
"Today, it shows me that I can do it, it was good to see my progression."
The Czech world number 23 now has a relatively simple quarter-final draw, playing world number 103 Su-Wei Hsieh in the next round.
Also facing a player with a three-digit ranking will be second seed Julia Goerges, who cruised into the quarter-finals with a 6-4, 6-0 victory over Slovakian qualifier Viktoria Kuzmova.
Goerges had struggled in the first round, needing three sets to beat Monica Puig, but she overwhelmed the 19-year-old Kuzmova, hitting nine aces and dominating on first serve to easily progress.
She will next play Slovenia's Polona Hercog, ranked 100th in the world, after Hercog knocked out Belgium's Kirsten Flipkens, 6-4 6-2. It was a bad day for the Belgians, with Ysaline Bonaventure also losing, going down 6-4, 6-3 to Hsieh.
There were no such problems for the young Americans left standing, with qualifier Sachia Vickery and wildcard Sofia Kenin both progressing to the quarter-finals.