Given that the character is known for only being able to utter a single phrase in English - 'I Am Groot' - one does have to wonder how much Diesel needs the sheet of script in front of him...
[Vin Diesel officially cast in Guardians of the Galaxy]
Diesel's Facebook page has long since become a hotbed of 'Guardians of the Galaxy' news. It was here that the actor himself kick-started the rumours linking him to Groot, by posting a photograph of the larger-than-life Marvel Comics character.
Despite months of rumours, Diesel was only officially confirmed for the role in December - and again, he marked this with a photograph.
Now, Diesel has used Facebook to point out a link between 'Guardians of the Galaxy' and an earlier piece of voice work which remains quite probably the most praised performance of the actor's career.
Alongside the image of himself in the booth, Diesel notes "Some of you may remember the character I voiced back in 1998…
"Last month I had the opportunity to voice a new character, on the Disney lot… and I was shocked to see the same sound engineer, Doc, who was there when Brad Bird was directing me 15 years earlier, as the Iron Giant.
"As artists we are susceptible to clocking omens... and this was a great sign."
Engineer Doc Kane has been in the business for 30 years, clocking up well over 300 screen credits, as well as being Oscar-nominated for his work on 'Beauty and the Beast,' 'Aladdin,' and Brad Bird's other animated movies 'The Incredibles' and 'Ratatouille.'
[First official image of Guardians of the Galaxy ]
It was noted by Comic Book Movie that Diesel concluded the post by declaring "This summer's Guardians of the Galaxy, is not only going to blow you away, it could very well break Marvel records. Grateful for the opportunity to make magic."
However, this he has since edited this to simply say the film is "going to blow you away."
And well he might. While hopes are certainly high that 'Guardians of the Galaxy' will prove a worthy addition to the Marvel movie universe, all bets are off as to how it will perform at the box office.
However this latest ambitious Marvel movie goes down, we might keep in mind that this may not be the only role Diesel will portray for the studio. Rumours persist he may still be in line for the cosmic super-villain Thanos, teased by the ending of 'Avengers Assemble' and expected to be the big bad of the third 'Avengers' movie.
Do you think Diesel is a good fit for Groot? Think he was right or wrong to suggest that 'Guardians of the Galaxy' could be one of Marvel's biggest movies yet? Sound off in the comments below.
Ben Bussey is a freelance writer and comic book movie/sci-fi fantasy/horror enthusiast. He considers 'The Iron Giant' to be far and away the best thing Vin Diesel has ever done, and hopes his work as Groot will come close to recapturing that vibe.