Home plans were thrown into disarray when volatile Gary Oakley declared himself unfit just before the game and then stunned Riga by announcing that he was quitting the club for a new playing career in Germany.
Riga responded by coming back from 10-7 down to take the first set 15-12.
Polonia levelled with a 15-11 success only for Riga to win the third set 15-9.
The visitors then took command, -however, and eased home 15-11 15-10 with Great Britain international Jurek Jankowski dominant.
Said Riga captain Tom Young: -"We were disappointed not to win. We lacked the killer instinct in that second set and paid the price. On the whole, though, we played better than against Leeds and it won't be long before we're back on the, winning trail"
