The 26-year old Fiji international has been brought in from Auckland City as injury replacement for Paul Ifill, who has a ruptured Achilles, and is set to become the first player from his nation to play in the A-League.
"Riera did a good, simple job in midfield winning the ball and passing it well, and he has made the transition from ASB Championship to A-League with some top-class performances.
"Krishna was quick with close technical skills and an eye for goal, and when I researched his record I was impressed.
"He seems the sort of player capable of taking the next step and scoring goals in the A-League."
Krishna previously spent time with Waitakere United, where he scored 72 goals in 103 appearances, and has also netted 14 times in 22 internationals for Fiji.
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