"Harinordoquy at number eight will be a dangerous running threat and Yachvili is one of the world's best number nines," Barnes told BBC Points West.
"Yachvili gets them going on the front foot so is someone we need to mark."
"As a player you have some opportunities to play against the best and this is very much one of them.
"Biarritz are a top side and finalists last year so to bring them here to the Rec for the opening match is something we all savour.
"They are a side that play a good structured game but are very, very happy playing an unstructured game.
"So it's up to us when we're defending to make sure we're controlling the ball and not giving their key players time on the ball."
The West Country side travel to Italy to face Heineken Cup new boys Aironi on Saturday, October 16 before back-to-back games against Ulster in December.