Francis will start at inside centre for England against USA on Thursday (kick-off 11.45am UK time).
The Saints star earned a place in Eddie Jones' squad following a fine campaign at Franklin's Gardens.
Francis, who moved to Northampton from Super Rugby side the Blues in 2017, established himself as the first-choice 12 at Saints last season, scoring seven tries in 23 appearances.
He has since cemented his place in the England squad and will win his ninth cap in the clash with the USA.
And Vesty said: "PF is a fantastic player because every time he's on the pitch you know he's going to give you absolutely everything he's got.
"He doesn't necessarily do the stand-out things in a game but he does everything really well.
"That level and consistency of performance is something that is real class. It's a real art form to get that.
"He's a real bit of glue to our attacking game and he's a real bit of glue to our defensive game."