The Mount are in second place on 36 points, and are somewhat of an unknown team, having to default to Rotorua-Lynmore earlier in the season.
"We don't fully know what to expect and that's hard to prepare for," Tamai said. "We just have to go in positive and with a strong game plan.
"Winning the first couple of match-ups is crucial. We need to keep our heads up throughout and power through."
Rotorua will field a strong squad - James Wilce (2), Jesse Galvin-Dawson (3), Sean Martin (4) and Campbell Brake as a reserve.
"We have real quality, strength and depth in this current side," Tamai said. "Everyone's service game has to be on point and we have to be hitting those lines with the winners.
"To take home that trophy would really seal a top year for this team."
Meanwhile, the Rotorua-Lynmore men's second team playoff for third place against Hamilton, at the Rotorua Tennis Club, after both sides finished on 29 points.
Waikato Bay regional premier senior interclub competitions
Premier Men's final:
Saturday, 1pm:
Rotorua-Lynmore 1 v Mount Maunganui Otumoetai, Rotorua Tennis Club.
Premier Men's third place playoff:
Saturday, 1pm
Rotorua-Lynmore 2 v Hamilton, Rotorua Tennis Club.