The 35-cap centre is contracted with Toulon until June 2017, however, club owner Mourand Boudjellal has stated he would be willing to release Mermoz during the current off-season.
Next in line is South African fullback Willie le Roux.
Le Roux acts as a second playmaker in the backline which would give Blackadder an element of familiarity, with the fullback's style similar to that of Crusaders star Israel Dagg.
The 26-year-old is one of the best in the world and the battle for his signing will be toughly contested within Europe.
Meanwhile, some of Blackadder's own are also preparing to face new challenges in Europe.
Nemani Nadolo will arrive in France this week to link up with Montpellier.
Meanwhile, former Canterbury and Highlanders back rower George Naoupu is also heading offshore with English club side Harlequins confirming the signing of the Kiwi this week.