The fighter lost to Canelo in a super-middleweight title battle last month and he can't see anybody being able to beat the Mexican in the ring.
Smith said: "I don't think anyone beats him. He may only lose if he keeps going up in weight but he's put a stop to that. His defence is just too good."
The English fighter believes Canelo makes his rivals "hesitate" during fights and praised him for his "very clever" jabs,
Smith told Sky Sports: "He is very clever in terms of the jab. He walks you down. With anybody else, you would jab. But he wants you to jab because he's a counter-puncher. So you don't throw as many jabs and while you are waiting, he closes the space down without throwing anything.
"Then he jabs and hits you. You think: 'How did that land?'
"He keeps you guessing all the time. You are hesitant."
Smith believe that Canelo's defence is particularly effective as he found it took away his best skills in the fight.
He explained: "His best asset was his presence and his defence. He was so hard to hit clean. When I was throwing he was riding them, making me miss. You aren't landing so you stop fully committing to shots.
"He takes away what you are good at."
Smith admits that he would "take more chances" in the early rounds if he got the opportunity to fight Canelo once again.
He said: "If I got another chance I'd gamble early. Fight fire with fire. I'd take more chances."