Jersey Joe Walcott defends his title against Joe Louis in 1951

Yeah, he has a chance, it's just not a good one.
Using their performances against Marciano as a reference point, Walcott had more stamina, more power, more durability, better reflexes and was much closer to his best shape than Louis was to his.
The reason I'm giving Louis some chance is his jab. As long as Louis doesn't just gas out and become a sitting duck, he can put Walcott on the back foot and take a points win by sniping him with the jab all night. It was good enough to turn a prime Charle's face into a hamburger and it was good enough to frustrate and clobber Walcott a few years before.
The biggest issue is Louis' conditioning for fifteen rounds and his reflexes. He might not even realize Walcott's right hand is heading for his face this time before its too late, and even if he has more stamina than in his fight against Charles, I doubt he will be all that effective past round 10 if Walcott makes him work enough in the previous rounds.
We also saw how impotent that right hand was at point blank range, so Walcott can always find safety by smothering and infighting if he gets in trouble. Forget about Louis tracking Walcott down and finishing if he somehow hurts him.

 

Joe gets his first win over Louis imo.
At this point Jersey is buzzing, he's top of the world.
Louis knows how hard a fight Walcott is, it's an hard hill for him to climb.
Walcott knocks him down a few times, gets himself a unanimous dec.

 

Louis is too far past it to beat Walcott at that point.