The Expendables 3 isn't great -but you knew that already. It's essentially Sylvester Stallone and Jason Statham shooting people's heads off, so it can't be good, but one little piece of inspired casting has ensured the movie will be at least filed under guilty pleasure, rather than utter disaster.

The Expendables 3The cast of 'The Expendables 3'

In the team's third outing, Barney (Stallone) and Christmas (Statham) come head-to-head with Conrad Stonebanks (Mel Gibson) - the original founder of The Expendables who broke ranks and became a ruthless arms trader. In order to kill his former colleague, Barney must form a fresh team, recruiting individuals who are younger, faster and more tech-savvy. 

More: so, who leaked 'The Expendables 3'? - Lexi Alexander thinks she might know

More: check out the pictures from the Expendables 3 world premiere [pictures]

More: in defense of Bruce WIllis: why $4 million for The Expendables was a bargain

However, it is Gibson who injects fresh energy into this third movie - an actor who, despite his personal troubles, is still regarded as a hugely talented actor and - as demonstrated in The Expendables 3 - can play to his audience. 

"Thank goodness for Mel Gibson, who injects life in the third film of the Expendables franchise, which otherwise is a tired, turgid affair," said Louise Keller of Urban Cinefile.

The Expendables 3Sylvester Stallone in 'The Expendables 3'

"The Expendables 3 has its cake and shoots it: armed to the nipples with vast action and bulging A-listers, but over-over-blown and overcrowded. See it for Gibson's big-bad," said Simon Cook at Empire magazine.

"...probably the most eye-catching cast member is Mel Gibson, playing a murderous arms dealer," said Andrew Pulver of The Guardian. 

More: check out Sylvester Stallone's filmography 

During an interview promoting the movie with the Daily Review Atlas, Gibson said that, while he had fun shooting The Expendables 3, he was keen to return to directing - in which he has tasted success with Braveheart, The Passion of the Christ and Apocalypto. 

"I think my gift is directing, and I'm going to pursue that," he said, "I've got a few irons in the fire, but it doesn't pay to talk too much about it because industrial espionage is rife. The minute you say anything, somebody swipes the idea, and it ends up on TV. But that's OK, too. I'll direct TV. TV is getting amazing. I definitely have my sights set on more directing, and I will do it."

The Expendables 3 is set for release on August 15, 2015, despite leaking online several weeks ago.

Watch the featurette for 'The Expendables 3':