Born in Moscow, Krunić picked up a tennis racquet aged seven and trained at the glorious Spartak club. Moved to Belgrade, as a member of TK Red Star, she won the national club championships in 2008. That year she also became the youngest ITF title winner. In 2011 she won two crucial Fed Cup doubles against Canada and Slovakia bringing into the 2012 World Group. In 2011 she won her main draw WTA match in Budapest, as Nina Bratchikova retired, before losing to the third seed Klára Zakopalová. In 2012, she reached her first WTA quarterfinal in Tashkent.
She made her Grand Slam at 2013 Us Open, losing to Vandeweghe, and lived her breakthrough season in 2014. At Us Open she defeated good friend Piter, defeated No.27 Keys, although they both finished the match with the same amount of points, and No.4 Kvitova en route to R16 as a qualifier (l. Azarenka in three sets). Her best Grand Slam result to date helped her to make the Top 100 debut.
In 2015, she reached the third round at Wimbledon (d. No.35 Vinci and No.19 Errani, l. V.Williams) and the quarterfinals three times in Shenzhen, Bucharest and Linz completing her first top 100 season (at No.96)
In 2016 she passed $1 million in career prize money. She ccontinued to play a mix of WTA and ITF Circuit events, qualifying at seven tour-level events including Wimbledon and Us Open: her best result was a quarterfinal run in Rabat (as qualifier, l. Erakovic).
In 2017 she reached the quarterfinal of the season in Bogota (d. Duque-Marino, Soler-Espinosa, l. Arruabarrena). She gave her best in the Asian swing as she collected two further quarterfinals in Tokyo and Tashkent and finished runner-up in Guangzhou (l.Shuai Zhang).