Sharkey could make Ali miss but he was too aggressive to pull of the Jimmy Young type of spoiler win. It’s a good fight. Smaller men with speed and quality did bother Ali.
Jack Sharkey at his best had a skillset that was among the best. Unfortunately he tends to be remembered best for losing the title to Carnera, his very controversial title-winning bout with Schmeling, his draw with Mickey Walker, and getting KO'd in a battle he was winning against Dempsey. Also his last fight - a three round loss to a Joe Louis coming back from his loss to Schmeling. He is also remembered for being inconsistent - he could put up a brilliant battle or a mediocre one. He was at his best in the late 20s before he won the title, posting notable wins against the much-avoided and perennial no. 1 contender Harry Wills, and George Godfrey. And of course in the Dempsey fight we got to see both the best and worst in Sharkey. But since we are talking about the best Sharkey here, it is entirely possible that he might have won the Dempsey fight. He also outpointed Carnera in their first meeting. He was fast, clever, and a decent puncher in spite of his relatively low knockout percentage. His record also boasts a second round KO of Tommy Loughran, one of the cleverest boxers ever, and one who was very seldom stopped. Jack Sharkey had all the tools and on a good night was capable of upsetting almost anyone. Something else to consider - had Ali and Ken Norton never fought each other, what kind of arguments might be put forward to suggest that Norton would not only defeat Ali but give him all he could handle in three fights in hypothetical dream matches?
For all of his manifest failings, Sharkey was not one of the weaker lineal heavyweight champions. Not even close to the argument. The man has an embarrassment of good wins.