Hackett was taking part in the Contender Series, with a convincing win earning the victor a lucrative contract from UFC head honcho Dana White.

Despite the best efforts of previously unbeaten Hackett, that contract went to Leonardo.

Hackett, 21, got off to a strong start in the flyweight duel but Leonardo's experience (now 8-2-0) and superior grappling helped secure a second round technical knockout (TKO).

Hackett (now 3-1-1) opened the contest with some impressive front kicks up top and a few snapping blows to the legs.

But Leonardo was able to clinch and trip the action to the canvas, where she immediately started to strike from top position.

Hackett managed to get up and resume her standing attack with the two exchanging strikes until the end of the first round.

The young Australian, who is a former world Muay Thai boxing champion, regrouped and again tried to do some damage with her kicking gam, also landing some punches of her own which rattled her opponent.

Leonardo closed the distance to slow things down and eventually was able to return the action to the canvas, where she seized control.

Hackett did her best to escape the barrage but the referee called it off at the 4:41 mark of the second stanza, with Leonardo awarded the win.

The US fighter sufficiently impressed White and will now battle in the UFC women's flyweight division which is currently headed by champion Valentina Shevchenko.

Australian Associated Press