World record-holder Summer McIntosh failed to qualify for the 400m freestyle final at the Pan Pacific Championships in Irvine, California, on Friday, slumping to the ninth-quickest time in the heats.

As the year's biggest event begins, McIntosh is already firmly at the top of the sport. The question now is how much better can she get.

Australian Lani Pallister edged three-time Olympic gold medallist Summer McIntosh to win the women's 200m freestyle at the Pan Pacific Championships on Wednesday in Irvine,…