The UFC women's flyweight title fight that was planned for UFC 251 is off.

Valentina Shevchenko, the champion, is injured and out of the scheduled bout against Joanne Calderwood, Shevchenko confirmed Tuesday to ESPN. Calderwood first mentioned the cancellation in an interview with MMA Fighting.

UFC 251 is planned for June 6 in Perth, Australia. Shevchenko vs. Calderwood was set as the co-main event of the card.

Shevchenko told ESPN that she sustained a leg injury in her title defense against Katlyn Chookagian at UFC 247 in February that did not heal all the way. She said she believes she will be healthy and ready by the end of August.

Calderwood said she expects her title shot to be "pushed back" to another date, and that maybe that isn't the worst outcome due to the coronavirus pandemic not allowing fighters to access their gyms.

"It could be a blessing in disguise," Calderwood told MMA Fighting.

Shevchenko (19-3) is ranked ESPN's No. 2 pound-for-pound women's MMA fighter in the world. The Kyrgyzstan native has won five straight, with three flyweight title defenses. Shevchenko, 32, has lost to only one woman in the UFC: bantamweight and featherweight champion -- and current pound-for-pound queen -- Amanda Nunes twice.

Calderwood (14-4) has won two of her past three bouts. The Scotland native is coming off a split decision win over Andrea Lee at UFC 242 last September. Calderwood, 33, is ranked No. 4 among women's flyweight fighters by ESPN.

UFC 251 does not yet have a main event officially booked, though a featherweight title defense by Australia native Alexander Volkanovski is expected.