Boudjellal outrageously likened the former Western Force and Brumbies playmaker to the four time Ballon d'Or winner after Toulon welcolmed two-time World Cup winning All Black Ma'a Nonu this week.
With Quade Cooper, James O'Connor and Matthieu Basteraud already in the Toulon ranks, Nonu's arrival will create significant midfield competition, but Boudjellal insisted Giteau is virtually untouchable in the number 12 jersey.
Giteau helped the French powerhouse complete a three-peat of European Rugby Champions Cups this year and was a vital cog in the Wallabies' run to the RWC final in October.
"If you look at Toulon's statistics with and without Matt Giteau, they're not the same," Boudjellal said.
"It's like comparing Barcelona's statistics with and without Lionel Messi."
While Giteau has plenty of trophies at club level, he is the only player in rugby history to lose to World Cup finals (2003 and 2015).
Messi, with 105 international caps and 49 goals to his name has a World Cup silver medal (2014) as well as two Copa America runner-up gongs.
It seems their stellar club records aren't the only thing they have in common...