BIRMINGHAM, UK - The all-Pliskova derby in the second round of the Nature Valley Classic yesterday was the WTA Tour's first ever clash between twins in a main draw match - and it didn't disappoint, either in terms of tightness or drama.

Qualifier and elder twin Kristyna just about held off No.3 seed Karolina as the younger of the pair attempted to overturn a 1-4 final-set deficit, edging a nervy deciding tiebreak that had the crowd alternately gasping and groaning on her third match point. "Yes, the end was horrible," Kristyna laughed afterwards, recalling the consecutive double faults from each sister at 5-5 in the tiebreak. Asked about her next match against compatriot Barbora Strycova in the on-court interview, she had merely said: "If I got through that, I can get through anything!"

"We both were nervous," agreed Karolina. "I was not scared about losing or winning - but because we didn't face each other in so many years, so we just didn't know how it was going to be." 

Kristyna Pliskova (Jimmie48/WTA)

Though the pair had played each other in 10 previous official matches - once in juniors, eight times in ITF tournaments and most recently before today in Eastbourne qualifying in 2013 - neither drew much on this intertwined history today: Kristyna had needed to look up their head-to-head online to remember when they had last played, and had no recollection of their junior clash, in the semifinals of a Grade 5 event in Malta in 2006. Karolina, meanwhile, said that despite growing up playing against each other, she no longer had any special knowledge about her sister's game - due to their agreement a few years ago to keep their relationship as tennis-free as possible.

"We didn't practice that much for the last couple of years," the Rome champion revealed. "We just talked before [that] it is not the best idea to spend too much time on court together because off the court, we are always together. So in the last three, four years we didn't play many games - maybe one or two, maybe sometimes more practicing but not really points."

Karolina Pliskova (Jimmie48/WTA)

Tactically, Karolina divulged that while she had been wary of her sister's booming serve, which tallied 24 aces today - "You cannot leave open some corners to her serve, but she can serve anywhere so that is where she is dangerous" - she had thought her opportunities would come in other areas. "From the rally, I thought I was better," assessed the former World No.1. Nonetheless, the end result was, on paper, one of the biggest upsets of the year: at No.112, Kristyna is the lowest-ranked player that Karolina has lost to since falling to Vera Zvonareva in Moscow last October, while Karolina has become the first ever Top 5 win of Kristyna's career.

Not that either put much stock in the other's ranking. "I don't see her as a top three player, just my sister," shrugged Kristyna. "If I would beat someone [else] No. 1 or No. 2, I would be extremely happy, but like this I'm normal." 

Karolina, meanwhile, acknowledged: "There is a big gap between us in the rankings, so I should have won easily, or whatever - maybe everybody thought that." However, there were a couple of complicating factors. "I think she should not really be ranked where she is," the 2016 US Open runner-up continued. To date, Kristyna has won just won WTA title - Tashkent 2016 - compared to Karolina's 13, and has just a pair of third-round showings at a major compared to Karolina's seven runs to the quarterfinals or further. "She needs to improve," said Karolina. "But if she is playing like today, she can beat most of the players." 

The other leveller was grass. Indeed, although the twins' professional head-to-head is now all square at 5-5, Kristyna has won all three of their grass encounters. "Grass is a really different story," said Karolina. "Her serve is super-effective on grass." Kristyna was in agreement: "My serve on grass is a big weapon so I don't think it would be like this on any other surface - but on grass, yes, I feel good," she said.

The Pliskovas have taken the opportunity of playing the same tournament this week to spend as much of their time together as possible, and having to play each other didn't change a thing: the sisters went for dinner and a shopping trip in Birmingham's Bullring mall the previous night, ate both breakfast and lunch together on the day of the match - and struck a deal over what would happen after it.

"Whoever wins is buying something for the other one," announced Karolina. "So I get a present!" Kristyna, however, remembered it slightly differently. "She is richer than me," the victor pointed out, laughing. "We said if she wins, she's going to give me all her prize money. But if I win, I just buy a present, it's true."

Regardless, despite the stress of the day, there was never any question of the match affecting the twins' relationship. "Look, she's my sister," said Karolina. "It doesn't matter if she beats me, or if I win, it will continue to be this way - so the tennis should not be in the way."