The World number two Indian took 40 minutes to pack off Juan, ranked 21, 21-14 23-21 in the women's singles competition at the Singapore Indoor Stadium to record her fifth victory over the local player.
The 23-year-old from Hyderabad will next take on Japanese Eriko Hirose, who holds a 3-2 record against the Indian. The world number 12 had spoilt Saina's All England campaign when she beat her in straight games in the quarterfinals in the 2011 edition.
In the second game, Juan was impressive as she held a 10-5 lead early on but Saina bounced back to level par at 12-12. After a brief fight, Saina was successful in grabbing the lead at 19-16 but Juan didn't want to go down without a fight.
The Singaporean produced a four-point burst to lead 20-19 but it was Saina who had the last laugh in the end.