With Riga assured of a top flight place next year and ex-England International, Mike Percival, back in the squad, the game should have allowed the side to show what it can really do.
All seemed to be going to plan when the hosts went 6-2 up through wonderful play by Pascal Cottet and skipper Tom Young.
But Sheffield struck back to take six points in a row thanks to powerful serving by their captain and Warwick compounded the situation to gift the set easily 15-9.
An injury to Ben Bunn during the second set disrupted Riga's rhythm and their mini-revival after he returned to the court following treatment, was too little, too late, as they missed out 15-12.
The visitors were by now full of confidence and quickly cancelled out Riga's slender lead in final set to run out deserved 15-9 winners.
"To say we weren't at our best is an understatement," said Riga captain Tom Young.
"We just weren't at the races and have got a lot of hard work to do before next season if we don't want a repeat of that sort of performance."
