Vimal Kumar was Saina's coach when she attained the World No.1 ranking in 2015.
After losing her two meetings against Marin, it was third time lucky for Saina.
The 28-year-old Indian, who was a runner-up here last year, notched up a 18-21 21-12 21-18 win over sixth seed Bingjiao, a world championship bronze medallist.
Nehwal will now face the winner of the quarterfinal match between Chen Xiaoxin and He Bingjiao.
Sindhu, seeded second, defeated Tunjung 23-21, 21-7 in 37 minutes to make the last-eight stage of her season-opener.
Commonwealth Games bronze medallist pair of Ashwini Ponnappa and N Sikki Reddy also bowed out of the competition, losing 14-21 14-21 to Thailand's Jongkolphan Kititharakul and Rawinda Prajongjai