Defoe scored Sunderland’s last two goals in their 3-1 win over Villa, to provide them with a crucial three points.
Sam Allardyce’s men stopped a run of five straight defeats by winning against the Claret and Blues.
And Cascarino said: “Jermain Defoe deserves a lot of credit. Despite making so many individual mistakes Aston Villa were the better footballing team, but Defoe took every opportunity presented to him.
“Sunderland worked much more like a Sam Allardyce team, they didn't give much away during the game.”
Sunderland took the lead against Villa when Patrick van Aanholt scored with a deflected shot.
However, they were pegged back when Carles Gil hit a wonderful volley into the back of the net in the second half.
At that point, Remi Garde’s side looked the more likely victors - but Sunderland struck back, with Defoe highlighting his lethal finishing once again.
The veteran forward had been on the fringes for much of the match, but he took his two opportunities with aplomb.
Defoe has now scored nine times in 17 appearances this season. He is the leading scoring at the Stadium of Light.