And Mariner expects the duo, together with Craig Noone, to challenge Chris Clark for a starting role.
"Bolasie is doing very well," Mariner told the club's official website. "Damien is back and we've got Nooney and Yala, so we have a lot of health going down the left-hand side.
"Clarky's done a fantastic job for us but this is football and everybody needs to be pushed.
"The thing with Yala is that we just need him to work both sides of the ball and we're driving that home to him."