Walker died after the sports car he was riding in crashed in Santa Clarita, California last November, leaving friends, family and fans in complete shock.
Vin Diesel and Paul Walker worked together for years after appearing in the first 'The Fast And The Furious' film back in 2001, reported Daily Express.
"It's one of the darker moments in this, in my journey. It's a rough one. It's a heavy thing. I grew up in the bouncer world, and we lost people while we were bouncing. But the brotherhood in Paul Walker was something completely different," Diesel said.
The star, who is currently promoting his latest film 'Guardians Of The Galaxy' added, "We grew up in the business together, and we became famous together. We represented the biggest franchise together. He was my partner.
"I've been acting all my life and they don't teach you in acting, how to mourn someone and simultaneously pretend they're in a scene with you," he added.
Paul's brothers Caleb and Cody were hired to fill-in in scenes featuring his character Brian when shooting resumed in March following a four-month hiatus, and filming wrapped last month.